Session Handoff: Realistic Sounds for Guide Tracks

Context

The Slow Aurora guide tracks are MIDI arrangements rendered through FluidSynth + MuseScore General soundfont. Current state: all GT rules (GT-1 through GT-10) are baked into COMPOSITION_PROCESS.md and the 3 AM cron. The arranger script (midi-arranger-v5.py) supports onset_offset_ms, pan, reverb_send, and numeric program changes.

Problem

The MuseScore General and GeneralUser GS soundfonts both have struck-decay envelopes on every patch. Notes decay 9+ dB within 1 beat regardless of instrument type. Re-articulation masks this but doesn't solve the underlying issue: the guide tracks sound like a cheap MIDI synth, not real instruments. The goal is realistic-sounding guide tracks that give Suno a better audio reference.

What to explore in the next session

1. Higher-quality soundfonts - MuseScore General (297 MB) and GeneralUser GS (32 MB) both decay. Try FluidR3 GM (140 MB), SGZillbaSound, or Arachno Soundfont. Check if any have proper sustain for bass, strings, and pad patches. 2. Soundfont installation - Download candidate soundfonts to `projects/the-slow-aurora/soundfonts/`. Test each with the audibility test v3 JSON (5 instruments isolated, 4 beats each). 3. Alternative render engines - FluidSynth is the current engine. Consider: - Timidity++ (different synth engine, may handle sustain better) - lmms or ZynAddSubFX for per-instrument patch control - MuseScore 4's own renderer (different soundfont engine) 4. Per-instrument soundfont rendering - Render each track with a soundfont that suits it, then mix the stems. Bass needs a synth bass with proper sustain, pad needs a warm pad that holds, etc. 5. Suno Audio Influence reality check - Does the guide track quality actually matter for Suno's output? Test: generate with the current v7 guide track vs. a version with better sounds, and compare Suno's output quality. 6. Re-articulation in the v7 guide track - The v7 guide-track.json has NOT been updated with re-articulation. Bass, strum, and harmonics notes longer than 2 beats need overlapping re-strikes per GT-10.

Files

Arranger: `projects/the-slow-aurora/scripts/midi-arranger-v5.py`
Process: `projects/the-slow-aurora/COMPOSITION_PROCESS.md` (GT-1 through GT-10)
Audibility test JSON: `projects/the-slow-aurora/days/2026-07-30-force-0330/audibility-test-v3.json`
v7 guide track JSON: `projects/the-slow-aurora/days/2026-07-30-force-0330/guide-track.json`
Soundfonts dir: `projects/the-slow-aurora/soundfonts/`
check_render: `projects/the-slow-aurora/scripts/check_render.py`
3 AM cron: job ID `3e91f0b3-6407-4cca-a4dd-e61401193096`
Daily memory: `memory/2026-07-30.md`

Key decisions from this session

Program change bug: arranger was defaulting all instruments to piano (program 0). Fixed - now reads numeric `instrument` field.
Strum minimum: A5 (880 Hz). E5 (659 Hz) inaudible.
Pad A3 prohibition: use B3/C4/E3 instead.
Normalization: render WITH `--normalize` (was `--no-normalize`).
De-fusion: onset stagger, pan spread, reverb send, velocity discipline (GT-8).
Re-articulation: bass/strum/harmonics must re-articulate notes >2 beats (GT-10).
GeneralUser GS has same decay as MuseScore General - not a fix.

Starting prompt for next session

"Read the session handoff at `projects/the-slow-aurora/days/2026-07-30-force-0330/session-handoff-realistic-sounds.md`. The goal is to make guide tracks sound like real instruments, not a cheap MIDI synth. Current soundfonts (MuseScore General, GeneralUser GS) have struck-decay envelopes that make every instrument fade within 1 beat. Explore better soundfonts, alternative render engines, or per-instrument stem rendering. Test with the audibility test JSON at `projects/the-slow-aurora/days/2026-07-30-force-0330/audibility-test-v3.json`. Also update the v7 guide track with re-articulation (GT-10) and re-render with the program fix."