An informal trial · 26–28 September 2026 · David Reinstein

Can AI write a modern jazz tune?

Two rounds. In round 1 I gave three AI agents the same prompt: an original, bright post-bop tune with a two-chorus trumpet and guitar duo solo over its changes, plus sheet music, MuseScore files and an iReal Pro chart. In round 2 two agents got a darker brief: a jazz waltz, a duo built on classical counterpoint, and a solo etude. Have a listen, then tell me which you prefer.

Feedback welcome on the page itself: select any text to comment with Hypothes.is (the sidebar on the right). I read every note.

TL;DR: just hear the recordings

These are mocked-up recordings of each run’s own sheet music. The order is shuffled for each visitor, and nothing up here says which AI wrote which. If you’d like to listen blind, vote before reading the tune notes further down, which do.

Round 1: bright three agents, one prompt: a post-bop tune with lydian colour, and a trumpet and guitar duo

Recorded with one recipe: the audio instructions behind the Halation recording, applied unchanged to the other two. Trumpet on top, alto sax on the guitar line. Round-1 cards also link a video that follows the score with a bar-by-bar commentary on the theory (made with the earlier mix; see the playlist).

Halation

F lydian · ♩ = 184 · 32 bars · A B A′ C

Band recording: trumpet and alto sax, with piano, bass and drums 2:58

Watch with the score and a bar-by-bar theory commentary YouTube, earlier mix

How this recording was made and other versions

Made by the Halation session from one audio request: a better-than-MIDI recording with alto sax playing the guitar line. Its instructions are the recipe for the other two round-1 recordings. Trumpet: University of Iowa samples. Sax, piano, bass and drums: Apple GarageBand instruments, with a rhythm section generated from the chords. On 28 Sep the rhythm section was redone for every recording on this page, the same way: a softer ride cymbal and less repetitive drums, bass and piano.

The original band demo, before the rhythm-section update 2:58

As the Halation session first made it, with the louder ride and simpler drums.

Lead sheet (PDF) · Tune notes

Parallax

E♭ lydian · ♩ = 176 · 32 bars · A A B A

Band recording: trumpet and alto sax, with piano, bass and drums 3:12

Watch with the score and a bar-by-bar theory commentary YouTube, earlier mix

How this recording was made

Same recipe as the other two headline recordings: the audio instructions that produced the Halation recording, applied unchanged (code, samples, mix, random seed), at the composer's own tempo. Trumpet: University of Iowa samples. Alto sax (playing the guitar line), piano, bass and drums: Apple GarageBand instruments, with the rhythm section generated from the run's own iReal chart. Details: trial_recordings/README.md. On 28 Sep the rhythm section was redone for every recording on this page, the same way: a softer ride cymbal and less repetitive drums, bass and piano. Parallax's written 4-bar guitar intro is left out (the recipe's intro is a rhythm-section vamp); its written coda ends the recording.

Lead sheet (PDF) · Tune notes

Glass Meridian

F major, lydian colour · ♩ = 164 · 32 bars · A A2 B C

Band recording: trumpet and alto sax, with piano, bass and drums 3:20

Watch with the score and a bar-by-bar theory commentary YouTube, earlier mix

How this recording was made and other versions

Same recipe as the other two headline recordings: the audio instructions that produced the Halation recording, applied unchanged (code, samples, mix, random seed), at the composer's own tempo. Trumpet: University of Iowa samples. Alto sax (playing the guitar line), piano, bass and drums: Apple GarageBand instruments, with the rhythm section generated from the run's own iReal chart. Details: trial_recordings/README.md. On 28 Sep the rhythm section was redone for every recording on this page, the same way: a softer ride cymbal and less repetitive drums, bass and piano.

The run's own v1: trumpet and guitar as written, over an iReal Pro rhythm section 3:16

This run's first recording, made from a single audio request (like the others, but without the ask to swap guitar for sax). Trumpet: VSCO 2 samples. Guitar: Apple's sampled Strat. Rhythm section: iReal Pro.

The run's own v3: trumpet and alto sax, programmed band, fuller bass 3:16

After three more rounds of my feedback: a more natural sound, sax instead of guitar, a less clichéd swing feel and a fuller upright bass. The other two got one audio request each, so this version had extra help.

Lead sheet (PDF) · Tune notes

Round 2: dark two agents, one prompt: a jazz waltz with Phrygian, sus♭9 sounds, a counterpoint duo and a solo etude

Each session also made its own recording from one identical audio request: clarinet on the top line, trombone on the lower one.

Tenebrae

D phrygian · ♩ = 138 · 32 bars · A A′ B C

Band recording: clarinet and trombone, with piano, bass and drums 4:25
How this recording was made

Made by the session that wrote the tune, from one audio request in the same words for both waltzes: clarinet on the top line, trombone on the lower line, adapting the round-1 recording engine to 3/4. Clarinet: Apple GarageBand samples; trombone: University of Iowa samples; piano, bass and drums: Apple GarageBand. Afterwards, by hand and the same for both waltzes: the bass raised 4.5 dB. On 28 Sep the rhythm section was redone for every recording on this page, the same way: a softer ride cymbal and less repetitive drums, bass and piano.

Lead sheet (PDF) · Tune notes

Noctilucent

E, phrygian colour · ♩ = 144 · 32 bars · A B A′ C

Band recording: clarinet and trombone, with piano, bass and drums 4:13
How this recording was made

Made by the session that wrote the tune, from one audio request in the same words for both waltzes: clarinet on the top line, trombone on the lower line, adapting the round-1 recording engine to 3/4. Clarinet: Apple GarageBand samples; trombone: University of Iowa samples; piano, bass and drums: Apple GarageBand. Afterwards, by hand and the same for both waltzes: the bass raised 4.5 dB. On 28 Sep the rhythm section was redone for every recording on this page, the same way: a softer ride cymbal and less repetitive drums, bass and piano. This one's clarinet was also raised about 2 dB, with its softest passages lifted, after a listen.

Lead sheet (PDF) · Tune notes

Which do you prefer?

All five are in the vote. One vote per browser, and you can change it later. You’ll see how others voted once you’ve voted. (Round 2 joined the vote on 28 September; earlier votes covered round 1 only.)

Your favourite overall
Rate each one (optional; 1 = weak, 5 = strong)
Halation round 1, bright
Parallax round 1, bright
Glass Meridian round 1, bright
Tenebrae round 2, dark
Noctilucent round 2, dark
What did you do? (optional)

What this is

Round 1: one evening I gave the same composition prompt to three AI coding agents: two separate Claude Code sessions running Claude Opus 5.5 at max effort, and one Codex session running GPT-6 Astra. Each worked in its own folder of my music repo, and the whole thing took about an hour, with a few follow-up prompts about audio.

Round 2: a day later I wrote a darker brief (a jazz waltz, classical counterpoint in the duo, and a technique-by-technique solo etude) and gave it, word for word, to one Claude Opus 5.5 session and one GPT-6 Astra session, each run unattended under matched conditions. Round 2 is the cleaner comparison of the two; see How it was made.

This is far from a clean trial, benchmark or comparison. I’m sharing it because the results are interesting to read and, I hope, to play.

Caveats
  1. One attempt per setup. The two Claude sessions share an opening move but otherwise came out quite differently, so a single run says little about a model.
  2. The follow-ups differed, mostly about audio. The Codex run got four rounds of audio feedback; the other two got one audio request each. See How it was made.
  3. Nobody has played these or rated them blind. The descriptions of motifs and devices come from each run’s own notes; treat them as claims to check against the scores.
  4. The recordings are programmed sample performances, not people playing. After listening I had some things fixed by hand (a louder bass, a softer ride cymbal, less repetitive drums, bass and piano), always the same way for every tune in a round.
  5. This was an hour of me switching between windows, and the prompts have my typos in them.

Play them, and get in touch

  • Record one yourself. I’d love it if people recorded these with real instruments: any line-up, any tune, the head or the duo choruses. I may try some myself: they’ll go on my YouTube playlist (short link bit.ly/jazztuba), alongside the recordings on this page. To share a recording, put a link in the comment box of the vote form above (only I can read those comments), email daaronr@gmail.com, or tag or DM me wherever you found this page.
  • Who did this. David Reinstein set up and ran this project: the prompts, the follow-ups, the fairness rules for the recordings and this page. The music, sheets and recordings were made by the AI agents described below.
  • Not an Unjournal project. This isn’t directly related to The Unjournal, where I work on open, public evaluation of research. But if it catches your interest, I’m happy to use it to point you there, and I’d welcome your attention and support for that work.
  • Jazz AI benchmarking. If you’d like to support or help build a more careful version of this, a proper benchmark of what AI can do in jazz composition, let’s discuss it further: email me at daaronr@gmail.com. This is a personal project, not an Unjournal one.

The five tunes and their sheets

Each card says which AI wrote the tune. Open the folds for the PDFs, recordings, editable files and the iReal Pro chart.

Round 1: bright

Halation

Claude Opus 5.5, max effort · Claude Code · session 1

F lydian · ♩ = 184 · 32 bars · A B A′ C

First page of the Halation lead sheetOpen the lead sheet (PDF)

Watch the video: the score, with the theory bar by bar

The idea, per the run’s own notes

Two motifs: a “bloom,” where the ♯11 comes in on the and of one and rings, and a cell built from F and G triads (A–C–G–D). The same B natural is the ♯11 of Fmaj7♯11 and then the ♯5 of E♭maj7♯5. The last two bars are a Lady Bird-style turnaround with every chord lydian.

Sheet music (9 PDFs)

Solo parts come one chorus per sheet.

Recordings
Band recording: trumpet and alto sax, with piano, bass and drums 2:58

Made by the Halation session from one audio request: a better-than-MIDI recording with alto sax playing the guitar line. Its instructions are the recipe for the other two round-1 recordings. Trumpet: University of Iowa samples. Sax, piano, bass and drums: Apple GarageBand instruments, with a rhythm section generated from the chords. On 28 Sep the rhythm section was redone for every recording on this page, the same way: a softer ride cymbal and less repetitive drums, bass and piano.

The original band demo, before the rhythm-section update 2:58

As the Halation session first made it, with the louder ride and simpler drums.

Editable files and the iReal Pro chart

Download the files (.zip)

MusicXML for any notation program, MuseScore files with the engraved layout, and the iReal Pro import page.

Paste it into Safari on a phone, tablet or Mac that has iReal Pro, or open the iReal page from the zip.

Parallax

Claude Opus 5.5, max effort · Claude Code · session 2

E♭ lydian · ♩ = 176 · 32 bars · A A B A · intro and coda

First page of the Parallax lead sheetOpen the lead sheet (PDF)

Watch the video: the score, with the theory bar by bar

The idea, per the run’s own notes

An F major triad stays put while the bass moves under it (E♭, D♭, B, B♭), so the same notes sound lydian, lydian augmented, altered and plain major in turn. Each restatement comes in an eighth note later than the last. The duo score has small notes naming the device in use (triad pair, displacement, hocket and so on).

Sheet music (7 PDFs)

Each part has chorus 1 on page 1 and chorus 2 on page 2.

Recordings
Band recording: trumpet and alto sax, with piano, bass and drums 3:12

Same recipe as the other two headline recordings: the audio instructions that produced the Halation recording, applied unchanged (code, samples, mix, random seed), at the composer's own tempo. Trumpet: University of Iowa samples. Alto sax (playing the guitar line), piano, bass and drums: Apple GarageBand instruments, with the rhythm section generated from the run's own iReal chart. Details: trial_recordings/README.md. On 28 Sep the rhythm section was redone for every recording on this page, the same way: a softer ride cymbal and less repetitive drums, bass and piano. Parallax's written 4-bar guitar intro is left out (the recipe's intro is a rhythm-section vamp); its written coda ends the recording.

Editable files and the iReal Pro chart

Download the files (.zip)

MusicXML for any notation program, MuseScore files with the engraved layout, and the iReal Pro import page.

Paste it into Safari on a phone, tablet or Mac that has iReal Pro, or open the iReal page from the zip.

Glass Meridian

GPT-6 Astra · Codex desktop app

F major, lydian colour · ♩ = 164 · 32 bars · A A2 B C

First page of the Glass Meridian lead sheetOpen the lead sheet (PDF)

Watch the video: the score, with the theory bar by bar

The idea, per the run’s own notes

A four-note cell (A–C–G–B) that comes back over different roots, in longer note values and split between the players. F and G triads give the lydian colour, and the bridge moves to E major.

Sheet music (9 PDFs)

Each part has chorus 1 on page 1 and chorus 2 on page 2. The guitar part is written at sounding pitch, not the usual octave up.

Recordings
Band recording: trumpet and alto sax, with piano, bass and drums 3:20

Same recipe as the other two headline recordings: the audio instructions that produced the Halation recording, applied unchanged (code, samples, mix, random seed), at the composer's own tempo. Trumpet: University of Iowa samples. Alto sax (playing the guitar line), piano, bass and drums: Apple GarageBand instruments, with the rhythm section generated from the run's own iReal chart. Details: trial_recordings/README.md. On 28 Sep the rhythm section was redone for every recording on this page, the same way: a softer ride cymbal and less repetitive drums, bass and piano.

The run's own v1: trumpet and guitar as written, over an iReal Pro rhythm section 3:16

This run's first recording, made from a single audio request (like the others, but without the ask to swap guitar for sax). Trumpet: VSCO 2 samples. Guitar: Apple's sampled Strat. Rhythm section: iReal Pro.

The run's own v3: trumpet and alto sax, programmed band, fuller bass 3:16

After three more rounds of my feedback: a more natural sound, sax instead of guitar, a less clichéd swing feel and a fuller upright bass. The other two got one audio request each, so this version had extra help.

Editable files and the iReal Pro chart

Download the files (.zip)

MusicXML for any notation program, MuseScore files with the engraved layout, and the iReal Pro import page.

Paste it into Safari on a phone, tablet or Mac that has iReal Pro, or open the iReal page from the zip.

Round 2: dark

Tenebrae

Claude Opus 5.5, max effort · Claude Code, headless

D phrygian · ♩ = 138 · 32 bars · A A′ B C · intro and coda

First page of the Tenebrae lead sheetOpen the lead sheet (PDF)

Watch the video: the score, with the theory bar by bar

The idea, per the run’s own notes

Everything grows from the half step above the root: D7sus(♭9) puts E♭ over D, and the first gesture is that E♭ sighing down to D. In the B section the dominants fall by half steps while the melody climbs against them across the barline; the C section is a lament over Dm(maj9). The duo is written as a fugato, canon, suspensions and stretto, and the etude works through one technique per 8 bars. Named after the Holy Week service in which the candles go out one by one.

Sheet music (12 PDFs)

Concert pitch and B♭ trumpet throughout; the study scores print the analysis under the staff. The packet has concert pitch first.

Recordings
Band recording: clarinet and trombone, with piano, bass and drums 4:25

Made by the session that wrote the tune, from one audio request in the same words for both waltzes: clarinet on the top line, trombone on the lower line, adapting the round-1 recording engine to 3/4. Clarinet: Apple GarageBand samples; trombone: University of Iowa samples; piano, bass and drums: Apple GarageBand. Afterwards, by hand and the same for both waltzes: the bass raised 4.5 dB. On 28 Sep the rhythm section was redone for every recording on this page, the same way: a softer ride cymbal and less repetitive drums, bass and piano.

Editable files and the iReal Pro chart

Download the files (.zip)

MusicXML for any notation program, MuseScore files with the engraved layout, and the iReal Pro import page.

Paste it into Safari on a phone, tablet or Mac that has iReal Pro, or open the iReal page from the zip.

Noctilucent

GPT-6 Astra, xhigh effort · Codex CLI, unattended

E, phrygian colour · ♩ = 144 · 32 bars · A B A′ C · 2-bar ending

First page of the Noctilucent lead sheetOpen the lead sheet (PDF)
The idea, per the run’s own notes

Centred on E with F natural on top: E7sus(♭9) and Fmaj7♯11/E share an E pedal and swap upper structures. The main motif is E–F–B–A (a half step, a tritone leap and a step down). The duo uses imitation, contrary and oblique motion, prepared dissonance and voice exchange, and the trumpet study has eight labelled technique blocks. Named after clouds that glow after sunset.

Sheet music (10 PDFs)

Concert pitch and B♭ trumpet; the B♭ duo score keeps concert chord symbols for the guitarist. Parts have one chorus per page.

Recordings
Band recording: clarinet and trombone, with piano, bass and drums 4:13

Made by the session that wrote the tune, from one audio request in the same words for both waltzes: clarinet on the top line, trombone on the lower line, adapting the round-1 recording engine to 3/4. Clarinet: Apple GarageBand samples; trombone: University of Iowa samples; piano, bass and drums: Apple GarageBand. Afterwards, by hand and the same for both waltzes: the bass raised 4.5 dB. On 28 Sep the rhythm section was redone for every recording on this page, the same way: a softer ride cymbal and less repetitive drums, bass and piano. This one's clarinet was also raised about 2 dB, with its softest passages lifted, after a listen.

Editable files and the iReal Pro chart

Download the files (.zip)

MusicXML for any notation program, MuseScore files with the engraved layout, and the iReal Pro import page.

Paste it into Safari on a phone, tablet or Mac that has iReal Pro, or open the iReal page from the zip.

How it was made

What I asked for in round 1

Hover over or tap a line to see my exact words.

  • An original tune in the straightahead post-bop style, with harmonic and melodic ideas from the 1990s on
  • Some bright sounds, such as lydian triad pairs; melody and chord changes
  • A two-chorus duo solo on the same changes for trumpet and guitar: weaving, dropping in and out, lots of counterpoint, some dramatic lines, real theme development
  • Quote and play with the melody, a few classic licks (not too many), and modern devices such as pentatonic shifting, triad pairs and rhythmic displacement
  • The two solo choruses on separate sheets, with the trumpet in concert pitch and in B♭
  • Everything as PDF, as something MuseScore can import, and as an iReal Pro chart
The full prompt
(Create a subfolder and work on this there. Note, I'll be asking GPT to work in a different subfolder -- don't look at its work) Create an original jazz tune in the 'straightahead post-bop' style, incorporating some harmonic and melodic developments from the 1990s and beyond. At least some 'bright sounds' (e.g., lydian triad pairing). Melody and chord changes, etc. Also write a 2 chorus '2 instrument solo' for those same changes, for trumpet and guitar, weaving in and out of each other, entering and dropping out using extensive counterpoint, some dramatic lines, and substantial 'theme development' throughout this duo-solo. Should cite and play with the melody a bit, use a few 'classic licks' (but not too much), and some other modern melodic soloing approaches (see the folder/repo ... things like pentatonic shifting, triad pairs, rythmic displacement, etc.) Present the 2 choruses of solos in separate sheets. The trumpet one both in concert pitch and in Bb transposition. For all of this, give it it to me as a pdf as well as a format we can import into musescore score as well as a chord chart for Ireal.

The Codex copy said “I'll be asking Claude” where the Claude copies say “I'll be asking GPT.”

Round 2: what I asked for, and how it was run

Hover over or tap a line to see my exact words.

  • An original jazz waltz with a darker tonality and a Wayne Shorter-ish feel, with some Phrygian and sus(♭9) sounds
  • A two-chorus trumpet and guitar duo, leaning on classical counterpoint
  • Two more choruses for one instrument, demonstrating soloing techniques one 8-bar block at a time, each block labelled
  • The same formats as round 1: separate sheets, trumpet in concert and B♭, PDF, MuseScore, iReal
  • Then a recording: clarinet on the top line, trombone on the lower one, adapting the round-1 recording engine to a waltz
  • Dark, where round 1 was light. Round 1 asked for “bright sounds” (lydian triad pairs) in a post-bop tune. Round 2 asked for a darker jazz waltz with a Wayne Shorter-ish feel and Phrygian, sus♭9 sounds, a duo leaning on classical counterpoint, and two more choruses for one instrument that demonstrate soloing techniques 8 bars at a time.
  • Two runs, same conditions. Tenebrae: one Claude Code session, Claude Opus 5.5 at max effort, run headless on 27 September. Noctilucent: one Codex session, GPT-6 Astra at xhigh (its top setting), run unattended on 28 September. Each got the same two prompts, word for word, with no questions answered and no feedback in between.
  • Same starting knowledge. Both could use the four skills written after round 1 (composing, engraving, iReal charts, trial pages) and the round-1 folders and recording engine. Astra worked in a copy of the repo with no trace of Tenebrae. Each read its own memory notes from round 1.
  • One slip. Astra's recording step ran in the main repo by mistake (the command that continues a Codex session can't set a folder). Its tune was already finished; during the recording it saw the file names of Tenebrae's videos but opened none of them. Details in ai_jazz_trial/waltz_prompts/astra_logs/RUN_RECORD.md.
  • Hand fixes after listening, applied to both waltzes alike: the bass raised 4.5 dB, and the shared rhythm-section update (below). Noctilucent's clarinet was also raised about 2 dB because it dipped under the band.
  • Time taken. Tenebrae: 53 minutes to compose, 10 to record. Noctilucent: 27 minutes to compose, 16 to record.

The composition prompt, identical for both runs

(Create a subfolder and work on this there.)

Create an original jazz waltz (3/4) with a darker tonality and a Wayne Shorter-esque feel, e.g., with some Phrygian / sus(b9) sounds.  Melody and chord changes, etc.

Also write a 2 chorus '2 instrument solo' for those same changes, for trumpet and guitar, weaving in and out of each other, entering and dropping out, some dramatic lines, and substantial 'theme development' throughout this duo-solo.  This time focus a bit more on the principles of classical counterpoint, applied to jazz.

Then write 2 more choruses of solo on a single instrument (trumpet or tenor sax), and have that solo illustrate some of the techniques and approaches discussed, doing so block by block. For example: eight bars demonstrating chromaticism and enclosures, eight bars beat displacement and rhythmic shifting, eight bars using diminished-scale substitution for the dominant chords, eight bars triad pairs, eight bars using the fully altered scale, eight bars 'playing out' (e.g., with a minor scale raised a half step), etc.  Label each block on the score.

Present the 2 duo choruses and the 2 single-instrument choruses in separate sheets. The trumpet ones both in concert pitch and in Bb transposition.

For all of this, give it it to me as a pdf as well as  a  format we can import into  musescore score as well as  a chord chart for Ireal.

The recording prompt, sent to the same session afterwards

Once this is sorted, create an audio recording of this for me to listen back as an MP3, more towards band in a box than cheesy 8 bit midi.

For the recording only (not the score): make the top voice (the trumpet part) a clarinet, and the lower voice (the guitar part, and the single-instrument solo if it isn't already for the top voice) a trombone. Try to get the trombone to sound as realistic as possible -- valve or slide is fine; a valve trombone may articulate better. Same for the clarinet: natural, with some imperfections, attack and breath, not synthesized-sounding.

Don't build the audio tools from scratch: adapt the engine in trial_recordings/ at the repo root (the recipe used for the earlier trial's recordings; read its README) to 3/4 jazz waltz feel (bass, drums, piano comping) and to these instruments. Sample sources: Apple's Clarinet Solo Legato / Staccato (.exs, already installed, see engine/render.py for how instruments are loaded) and the University of Iowa MIS tenor trombone recordings (free download, same format the engine already reads for the Iowa trumpet). Keep it efficient -- I don't want to burn through a huge amount of quota on this.

Structure: short rhythm-section intro, head, the 2 duo choruses, the 2 single-instrument choruses, head out.
Prompts, in order, for each run

UK time. Round 1 ran on the evening of 26 September (times after 00:00 are the 27th) and every round-1 run started from the prompt above; round 2 ran on 27 and 28 September. Open a prompt to read it as I typed it. For the Codex run I’ve added the reasoning effort its log shows for each turn.

Halation

Claude Opus 5.5, max effort · Claude Code · session 1

  1. 22:27Write the tune and the duo solo
    Prompt as typed
    (Create a subfolder and work on this there. Note, I'll be asking GPT to work in a different subfolder -- don't look at its work) Create an original jazz tune in the 'straightahead post-bop' style, incorporating some harmonic and melodic developments from the 1990s and beyond. At least some 'bright sounds' (e.g., lydian triad pairing). Melody and chord changes, etc. Also write a 2 chorus '2 instrument solo' for those same changes, for trumpet and guitar, weaving in and out of each other, entering and dropping out using extensive counterpoint, some dramatic lines, and substantial 'theme development' throughout this duo-solo. Should cite and play with the melody a bit, use a few 'classic licks' (but not too much), and some other modern melodic soloing approaches (see the folder/repo ... things like pentatonic shifting, triad pairs, rythmic displacement, etc.) Present the 2 choruses of solos in separate sheets. The trumpet one both in concert pitch and in Bb transposition. For all of this, give it it to me as a pdf as well as a format we can import into musescore score as well as a chord chart for Ireal.
    Lead sheet, duo score and parts done by 23:23
  2. 23:21Make an MP3, with alto sax as the second voice
    Prompt as typed
    ONce this is sorted, use some audio/midi tools to create so create an audio recording of this for me to listen back as an MP3. Try to use more sophisticated tools that you can access more towards band in a box then cheesy 8 bit midi. for the recording only (not the score), make the second voice a saxophone rather than a guitar.
    Band demo (2:58), finished at 23:46
  3. 23:50A question about the K-house folder
    Prompt as typed
    wait -- what did you take from 'k-howuse'?
    A question, not a change to the tune

Parallax

Claude Opus 5.5, max effort · Claude Code · session 2

  1. 22:29Write the tune and the duo solo
    Prompt as typed
    (Create a subfolder and work on this there. Note, I'll be asking GPT to work in a different subfolder -- don't look at its work) Create an original jazz tune in the 'straightahead post-bop' style, incorporating some harmonic and melodic developments from the 1990s and beyond. At least some 'bright sounds' (e.g., lydian triad pairing). Melody and chord changes, etc. Also write a 2 chorus '2 instrument solo' for those same changes, for trumpet and guitar, weaving in and out of each other, entering and dropping out using extensive counterpoint, some dramatic lines, and substantial 'theme development' throughout this duo-solo. Should cite and play with the melody a bit, use a few 'classic licks' (but not too much), and some other modern melodic soloing approaches (see the folder/repo ... things like pentatonic shifting, triad pairs, rythmic displacement, etc.) Present the 2 choruses of solos in separate sheets. The trumpet one both in concert pitch and in Bb transposition. For all of this, give it it to me as a pdf as well as a format we can import into musescore score as well as a chord chart for Ireal.
    Lead sheets, duo score and parts done by about 23:35
  2. 23:32Make and host this page
    Prompt as typed
    After all of this is done, make and host a web page for this full 'can AI write a modern jazz tune' informal trial. It should link the outputs (both Claude Opus 5.5 max tunes and the one GPT Astra high) explain what I did (the prompt chains and enviromnment here and in Codex), summarize the instructions and link/fold/tooltip the full instructions, etc. I'll want to share it around (while keeping working on the project). This was a 60 minute project. Far from a clean trial, benchmark, or comparison. Use /david-writing-style
    A first version of this page
  3. 23:42Turn key parts of the process into skills
    Prompt as typed
    after this is done, remember to turn key elements of the process into 'skills'
    Four skills: notation, iReal charts, composition, trial pages
  4. 23:54Where's the Parallax recording?
    Prompt as typed
    where is the 'parralax' recording? I see the other 2 mp3s but not that one
    None had been asked for; one is being made from Halation's audio request
  5. 00:01Recordings first, host on Netlify, my usual style, add a vote
    Prompt as typed
    make the audio more prominient on the hosted page (give a "TLDR, just hear the recordings") consider hosting it on Netlify or github rather than here, and make the web page styling more in my usual style, and less 'night mode' Also give people a prominent option to rate and vote on the tunes (which do they prefer, etc?), and a 'see how others voted' page they see only after voting
    This page
  6. 00:04Put Glass Meridian's recording on equal terms; more folds and tooltips
    Prompt as typed
    when you can, adjust the glass_meridian recording to use the same audio instructions as the others, for fairness (you can note this and preserve the orig recording as an alternate link, with explanations. ) Btw, use folds and tooltips more.
    A shared rendering pipeline for all three, in progress

Glass Meridian

GPT-6 Astra · Codex desktop app

  1. 22:28Write the tune and the duo soloeffort: xhigh
    Prompt as typed
    (Create a subfolder and work on this there. Note, I'll be asking Claude to work in a different subfolder -- don't look at its work) Create an original jazz tune in the 'straightahead post-bop' style, incorporating some harmonic and melodic developments from the 1990s and beyond. At least some 'bright sounds' (e.g., lydian triad pairing). Melody and chord changes, etc. Also write a 2 chorus '2 instrument solo' for those same changes, for trumpet and guitar, weaving in and out of each other, entering and dropping out using extensive counterpoint, some dramatic lines, and substantial 'theme development' throughout this duo-solo. Should cite and play with the melody a bit, use a few 'classic licks' (but not too much), and some other modern melodic soloing approaches (see the folder/repo ... things like pentatonic shifting, triad pairs, rythmic displacement, etc.) Present the 2 choruses of solos in separate sheets. The trumpet one both in concert pitch and in Bb transposition. For all of this, give it it to me as a pdf as well as a format we can import into musescore score as well as a chord chart for Ireal.
    Head, duo score and parts done by 22:50
  2. 22:52Make an MP3, closer to Band-in-a-Box than 8-bit MIDIeffort: xhigh
    Prompt as typed
    Use some audio/midi tools to create so create an audio recording of this for me to listen back as an MP3. Try to use more sophisticated tools that you can access more towards band in a box then cheesy 8 bit midi
    v1: sampled trumpet and guitar over an iReal Pro rhythm section
  3. 23:19More natural; sax instead of guitar; quieter leadseffort: medium
    Prompt as typed
    create the mp3 file again but try to make it sound a bit more natural. Do you have to use irealpro sounds? Also, for the recording only, make the second voice a saxophone rather than a guitar. I guess the horn and gtr are also slightly too loud in the mix.
    v2, with the next prompt
  4. 23:23A less clichéd swing feeleffort: medium
    Prompt as typed
    and try to use a slightly more sophisticated 'swing concept' -- you are being a bit cheesy/basic/cliche with that 'triplet eighth notes thing'
    v2: alto sax, programmed drums, looser eighth notes
  5. 23:36A better upright bass; share the audio instructionseffort: high
    Prompt as typed
    improve the bass sound. I barely hear it, and it doesn't much like an upright bass so much -- I hear the attack but not much of the strings. Also share the 'instructions for creating audio' so I can pass that to the other attempts at this.
    v3, plus a written audio brief for the other runs
  6. 23:38Consider making skills out of the processeffort: high
    Prompt as typed
    also consider making 'skills' out of the key parts of this process
    Two reusable audio skills

Tenebrae

Claude Opus 5.5, max effort · Claude Code, headless

  1. 27 Sep 18:01Write the waltz, the duo and the etudeeffort: max
    Prompt as typed
    (Create a subfolder and work on this there.) Create an original jazz waltz (3/4) with a darker tonality and a Wayne Shorter-esque feel, e.g., with some Phrygian / sus(b9) sounds. Melody and chord changes, etc. Also write a 2 chorus '2 instrument solo' for those same changes, for trumpet and guitar, weaving in and out of each other, entering and dropping out, some dramatic lines, and substantial 'theme development' throughout this duo-solo. This time focus a bit more on the principles of classical counterpoint, applied to jazz. Then write 2 more choruses of solo on a single instrument (trumpet or tenor sax), and have that solo illustrate some of the techniques and approaches discussed, doing so block by block. For example: eight bars demonstrating chromaticism and enclosures, eight bars beat displacement and rhythmic shifting, eight bars using diminished-scale substitution for the dominant chords, eight bars triad pairs, eight bars using the fully altered scale, eight bars 'playing out' (e.g., with a minor scale raised a half step), etc. Label each block on the score. Present the 2 duo choruses and the 2 single-instrument choruses in separate sheets. The trumpet ones both in concert pitch and in Bb transposition. For all of this, give it it to me as a pdf as well as a format we can import into musescore score as well as a chord chart for Ireal.
    Lead sheet, duo, etude, study scores and packet, done by 18:55
  2. 18:55Record it: clarinet and trombone, adapting the round-1 engineeffort: high
    Prompt as typed
    Once this is sorted, create an audio recording of this for me to listen back as an MP3, more towards band in a box than cheesy 8 bit midi. For the recording only (not the score): make the top voice (the trumpet part) a clarinet, and the lower voice (the guitar part, and the single-instrument solo if it isn't already for the top voice) a trombone. Try to get the trombone to sound as realistic as possible -- valve or slide is fine; a valve trombone may articulate better. Same for the clarinet: natural, with some imperfections, attack and breath, not synthesized-sounding. Don't build the audio tools from scratch: adapt the engine in trial_recordings/ at the repo root (the recipe used for the earlier trial's recordings; read its README) to 3/4 jazz waltz feel (bass, drums, piano comping) and to these instruments. Sample sources: Apple's Clarinet Solo Legato / Staccato (.exs, already installed, see engine/render.py for how instruments are loaded) and the University of Iowa MIS tenor trombone recordings (free download, same format the engine already reads for the Iowa trumpet). Keep it efficient -- I don't want to burn through a huge amount of quota on this. Structure: short rhythm-section intro, head, the 2 duo choruses, the 2 single-instrument choruses, head out.
    Band recording, done by 19:05

Noctilucent

GPT-6 Astra, xhigh effort · Codex CLI, unattended

  1. 28 Sep 12:21Write the waltz, the duo and the etudeeffort: xhigh
    Prompt as typed
    (Create a subfolder and work on this there.) Create an original jazz waltz (3/4) with a darker tonality and a Wayne Shorter-esque feel, e.g., with some Phrygian / sus(b9) sounds. Melody and chord changes, etc. Also write a 2 chorus '2 instrument solo' for those same changes, for trumpet and guitar, weaving in and out of each other, entering and dropping out, some dramatic lines, and substantial 'theme development' throughout this duo-solo. This time focus a bit more on the principles of classical counterpoint, applied to jazz. Then write 2 more choruses of solo on a single instrument (trumpet or tenor sax), and have that solo illustrate some of the techniques and approaches discussed, doing so block by block. For example: eight bars demonstrating chromaticism and enclosures, eight bars beat displacement and rhythmic shifting, eight bars using diminished-scale substitution for the dominant chords, eight bars triad pairs, eight bars using the fully altered scale, eight bars 'playing out' (e.g., with a minor scale raised a half step), etc. Label each block on the score. Present the 2 duo choruses and the 2 single-instrument choruses in separate sheets. The trumpet ones both in concert pitch and in Bb transposition. For all of this, give it it to me as a pdf as well as a format we can import into musescore score as well as a chord chart for Ireal.
    Head, duo, study, parts and packet, done by 12:48
  2. 12:49Record it: clarinet and trombone, adapting the round-1 engineeffort: high
    Prompt as typed
    Once this is sorted, create an audio recording of this for me to listen back as an MP3, more towards band in a box than cheesy 8 bit midi. For the recording only (not the score): make the top voice (the trumpet part) a clarinet, and the lower voice (the guitar part, and the single-instrument solo if it isn't already for the top voice) a trombone. Try to get the trombone to sound as realistic as possible -- valve or slide is fine; a valve trombone may articulate better. Same for the clarinet: natural, with some imperfections, attack and breath, not synthesized-sounding. Don't build the audio tools from scratch: adapt the engine in trial_recordings/ at the repo root (the recipe used for the earlier trial's recordings; read its README) to 3/4 jazz waltz feel (bass, drums, piano comping) and to these instruments. Sample sources: Apple's Clarinet Solo Legato / Staccato (.exs, already installed, see engine/render.py for how instruments are loaded) and the University of Iowa MIS tenor trombone recordings (free download, same format the engine already reads for the Iowa trumpet). Keep it efficient -- I don't want to burn through a huge amount of quota on this. Structure: short rhythm-section intro, head, the 2 duo choruses, the 2 single-instrument choruses, head out.
    Band recording, done by 13:05
Recordings: who got which audio request

Two sessions got one audio request each, in the same words: make an MP3 with something closer to Band-in-a-Box than “cheesy 8-bit MIDI,” and swap the guitar for alto sax on the recording (not the score). Halation’s session got it at 23:21 and made the Halation recording.

So that the three can be heard on equal terms, the headline recordings of Parallax and Glass Meridian were then made by applying the Halation recording’s instructions unchanged: same code, samples, mix and random seed, each tune at its composer’s own tempo, with its own written ending.

On 28 September, after listening, I had the rhythm section redone for all five recordings on this page, in the same way: a softer ride cymbal, drums that change from bar to bar and phrase to phrase (fills, set-ups, a closed hi-hat or cross-stick on some sections), and bass lines and piano comping that repeat less. All three round-1 tunes were re-rendered with it, including Halation; its original demo is kept as an alternate on its card. The two round-2 recordings got the same change.

The Codex session got the first audio request at 22:52 (without the sax swap), then three more rounds of feedback: sound more natural, use sax instead of guitar, a less clichéd swing feel, and a fuller upright bass. Its own versions, v1 (trumpet and guitar) and v3 (trumpet and sax), are kept as alternates on the Glass Meridian card.

The chord changes side by side (both rounds), and a few things round 1 shares

Concert pitch, four bars to a line; two chords in a bar split it at beat 3. Chords with a ♯11 are marked, since I asked for bright lydian sounds.

Halation

A
Fmaj7♯11
Fmaj7♯11
E♭maj7♯5
E♭maj7♯5
D7sus(♭9)
D7alt
Gm9
C13sus
B
D♭maj7♯11
Cm7F7
B♭maj7♯11
B♭m7E♭7
Am7D7
A♭m7D♭7
Gm9
C7alt
A′
Fmaj7♯11
Fmaj7♯11
E♭maj7♯5
E♭maj7♯5
Em7♭5
A7(♭9)
Dm(maj7)
Cm7F7
C
B♭maj7♯11
E♭9(♯11)
Am7
D7alt
Gm9
G♭7(♯11)
Fmaj7♯11A♭maj7♯11
D♭maj7♯11G♭maj7♯11

Parallax

A
E♭maj7♯11
E♭maj7♯11
D♭maj7♯5
D♭maj7♯5
B7alt
B♭maj9
A♭m9
D♭13♯11
A
E♭maj7♯11
E♭maj7♯11
D♭maj7♯5
D♭maj7♯5
B7alt
B♭maj9
G♯m7♭5
C♯7alt
B
F♯m11F7♯11
Emaj7♯11
Dm11D♭7♯11
Cmaj7♯11
B♭m11A7♯11
A♭maj7♯11
Fm11
E7♯11
A
E♭maj7♯11
E♭maj7♯11
D♭maj7♯5
D♭maj7♯5
B7alt
B♭maj9
A♭m9
D♭13♯11

Glass Meridian

A
Fmaj9♯11
Fmaj9♯11
Em7♭5A7alt
Dm9
D♭maj9♯11
Cm9F13
B♭maj9♯11
Gm9C7alt
A2
Fmaj9♯11
E♭maj9♯11
Dm9G13♯11
Cmaj9♯11
Bm7♭5E7alt
Am9
A♭maj9♯11
Gm9C7alt
B
Emaj9♯11
Emaj9♯11
Gmaj9♯11
F♯m7♭5B7alt
Em9
A13♯11
Dm9G13♯11
Gm9C7alt
C
Fmaj9♯11
E♭maj9♯11
Dm9G13♯11
D♭maj9♯11C7alt
Fmaj9♯11
D7alt
Gm9C7alt
F6/9

Tenebrae

A
D7sus(♭9)
D7sus(♭9)
E♭maj7♯11
E♭maj7♯11
B♭maj7♯5
B♭maj7♯5
A7sus(♭9)
A7alt
A′
D7sus(♭9)
D7sus(♭9)
E♭maj7♯11
E♭maj7♯11
A♭maj7♯5
A♭maj7♯5
D♭maj7♯11
D♭maj7♯11
B
C7♯11
C7♯11
B7alt
B7alt
B♭7♯11
B♭7♯11
A7alt
A7alt
C
Dm(maj9)
Dm(maj9)
Dm(maj9)
Dm(maj9)
B♭maj7♯5
B♭maj7♯5
E♭maj7♯11
E♭maj7♯11

Noctilucent

A
E7sus(♭9)
E7sus(♭9)
Fmaj7♯11/E
Fmaj7♯11/E
Am9
C7alt
F♯m7♭5
B7alt
B
Em9
Gm9
B♭maj7♯11
A7alt
Dm9
F7alt
F♯m7♭5
B7alt
A′
E7sus(♭9)
E7sus(♭9)
Fmaj7♯11/E
E7sus(♭9)
A7♭9
Dm9
B7♭9
Em9
C
Cmaj7♯11
A♭maj7♯11
Am9
D7alt
Fmaj7♯11/E
E7sus(♭9)
F♯m7♭5
B7alt
  • All three are 32-bar medium-up swing tunes centered on F or E♭, and all three lean hard on maj7♯11 chords.
  • The two Claude sessions opened the same way: two bars of a maj7♯11 chord, then two bars of a maj7♯5 a whole step down (Fmaj7♯11 to E♭maj7♯5 in Halation, E♭maj7♯11 to D♭maj7♯5 in Parallax), with melody notes held across the change.
  • Halation (Claude) and Glass Meridian (GPT) start their melodies with nearly the same notes over F lydian: A–C–G–D in Halation, A–C–G–B–D in Glass Meridian.
HalationParallaxGlass Meridian
ModelClaude Opus 5.5 (max)Claude Opus 5.5 (max)GPT-6 Astra (Codex)
Tempo♩ = 184♩ = 176♩ = 164
FormA B A′ CA A B AA A2 B C
Around the head1st and 2nd endings; all-lydian turnaround4-bar guitar intro; codaNone; every pass ends on F6/9
Solo sheetsOne PDF per chorusOne PDF per part, a chorus a pageOne PDF per part, a chorus a page
Guitar notationTreble clef, sounds an octave lowerTreble clef, sounds an octave lowerWritten at sounding pitch
Notation done (file times)23:23About 23:3522:50
Setup
  • Round 1: all three ran on my Mac in one Git repo that already had some of my chart work in it. Each session made its own subfolder and was told not to look at the others.
  • Claude: two separate sessions in the Claude Code desktop app, both Claude Opus 5.5 at max effort.
  • Codex: the Codex desktop app with GPT-6 Astra. Its log shows reasoning effort “xhigh” for the composition and the first recording, then “medium” and “high” for the audio fixes.
  • The machine had MuseScore 3.6.2, iReal Pro and Python. All three wrote their own code to generate the notation and rendered their PDFs through MuseScore.
  • My prompt pointed to “the folder/repo” for soloing ideas and then trailed off. The Parallax session went looking and found the topic list from my weekly brass-practice generator (pentatonic pairs, triad pairs, displacement).