pi-agent
bac1bd5686
- SKILL.md: complete reference for creating 90s-style MIDI with Python/mido - drum_reference.md: full GM drum kit note mapping - compose_neon_dreams.py: 1.5 min A minor dance track at 128 BPM - neon_dreams.mid: compiled 6-track MIDI (drums, pads, bass, synth lead, piano)
169 lines
5.1 KiB
Markdown
169 lines
5.1 KiB
Markdown
---
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name: 90s-midi-composer
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description: Create authentic 90s-style MIDI music files with General MIDI/SC-55 aesthetic. Use when creating MIDI music, composing dance/electronic tracks, or making 90s retro-sounding songs.
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license: MIT
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compatibility: Linux with Python3, mido library
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---
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# 90s MIDI Composer
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Create authentic early-to-mid 90s-style MIDI music using Linux tools and Python + mido.
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## Prerequisites
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Install required tools (one-time setup, requires sudo):
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```bash
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sudo apt-get install -y fluidsynth fluid-soundfont-gm
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pip3 install --break-system-packages mido
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```
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## The Tool: Python + Mido
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Mido is a Python library for working with MIDI files. Key classes:
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- `MidiFile(ticks_per_beat=480)` — MIDI file container
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- `MidiTrack()` — list of Message objects (one per instrument)
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- `Message('note_on', note=N, velocity=V, channel=C, time=T)` — start a note
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- `Message('note_off', note=N, velocity=V, channel=C, time=T)` — stop a note
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- `Message('program_change', program=N, channel=C, time=T)` — change instrument
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- `Message('control_change', control=N, value=V, channel=C, time=T)` — CC control
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- `MetaMessage('set_tempo', tempo=μs_per_beat, time=0)` — set tempo (μs/beat)
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## Timing in Mido
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Mido uses **relative** timing. Each message has `time` = ticks since the previous one.
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```
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ticks_per_beat = 480 (PPQ)
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1 sixteenth-note = 120 ticks
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1 eighth-note = 240 ticks
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1 quarter-note = 480 ticks (1 beat)
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1 bar (4/4) = 1920 ticks (4 beats × 480)
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```
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### Absolute → Relative Conversion
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Build events with absolute tick offsets, then convert:
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```python
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def rel(items): # items = [(abs_tick, Message), ...]
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items.sort(key=lambda x: x[0])
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out, prev = [], 0
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for at, msg in items:
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msg.time = at - prev
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out.append(msg)
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prev = at
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return out
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```
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## Creating a Basic MIDI File
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```python
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from mido import MidiFile, MidiTrack, Message as M, MetaMessage
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PPQ = 480 # pulses per quarter note (ticks/beat)
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BPM = 128
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TEMPO = 60_000_000 // BPM
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mid = MidiFile(ticks_per_beat=PPQ)
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# Track 0: Tempo
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trk = MidiTrack()
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trk.append(MetaMessage('set_tempo', tempo=TEMPO, time=0))
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mid.tracks.append(trk)
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# Track 1: Drums (channel 10 = 9)
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drums = MidiTrack()
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# ... add drum messages ...
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mid.tracks.append(drums)
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mid.save('output.mid')
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```
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## 90s Aesthetic Guide
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### Essential GM Patches (General MIDI)
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| Patch | Name | 90s Role |
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|-------|-------------------|-----------------------|
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| 1 | Acoustic Grand | Piano / melodic |
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| 37 | Synth Bass 1 | Driving synth bass |
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| 59 | Brass Section | Hits, accents |
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| 80 | Lead 1 Synth | **Arpeggio lead** |
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| 88 | Pad 4 (Choir) | Warm atmospheric pads |
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| 49 | Strings | Harmonic texture |
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| 16 | Electric Piano 1 | Rhodes-style |
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### GM Drum Set (Channel 10 = channel 9)
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| Note | Voice | Note | Voice |
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|------|--------------------|------|--------------------|
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| 36 | **Kick 1** | 38 | **Snare 1** |
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| 42 | **Hi-hat closed** | 46 | Hi-hat open |
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| 49 | Crash cymbal | 57 | Tambourine |
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| 51 | Ride cymbal | 50 | Low bongo |
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### Classic 90s Dance Beat (120-140 BPM)
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```
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Kick on every quarter note (1, 2, 3, 4)
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Snare on beats 2 & 4
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Hi-hat on every eighth note
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Open hi-hat on off-beats for groove
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```
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### 90s Chord Progressions
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- **Am | F | G | E7** — vi-IV-V-I in C (the quintessential 90s pop progression)
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- **C | G | Am | F** — I-V-vi-IV (the "axis of awesome")
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- **Em | C | G | D** — vi-IV-I-V (melancholy 90s feel)
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- **Am | C | G | E7** — i-III-VII-V (minor-key drama)
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### Instrument Patterns
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- **Arpeggio lead**: 16th-note chords cycling root-3rd-5th-octave, ascending and descending
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- **Walking bass**: Quarter-note chord tone movement, alternating arpeggio directions
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- **Pad chords**: 3-voice voicings, hold ~90% of bar for smooth crossfading
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- **Piano melody**: Pentatonic or natural minor scale, sparse 4-note phrases per bar
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### Effects (Control Changes)
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- **Reverb**: CC91, value 40-80 (higher = more spacious hall)
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- **Chorus**: CC93, value 50-90
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- **Filter**: CC5 or CC74, value 40-127
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- **Expression**: CC11, value 100-127
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### Song Structure Template
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```
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Intro (4 bars) — Pads only, dreamy and sparse
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Verse (8 bars) — Drums enter, bass + pads + arpeggio (no piano)
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Chorus (8 bars) — Full arrangement, piano melody joins
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Bridge (4 bars) — Breakdown or key change
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Final Chorus (8 bars) — Return, full energy
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Outro (8 bars) — Drums simplify, piano arpeggio fade
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```
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At 128 BPM: 40 bars ≈ 1.25 minutes. Example: 48 bars = 1.5 minutes.
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### BPM Recommendations
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| Genre | Typical BPM |
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|--------------------|-----------|
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| 90s slow jam | 80-100 |
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| House / dance | 120-130 |
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| Trance / techno | 130-150 |
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| Drum & bass | 170-180 |
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## Playing MIDI Files
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```bash
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# With fluidsynth
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fluidsynth -a alsa /usr/share/sounds/sf2/FluidR3_GM.sf2 output.mid
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# On macOS
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fluidsynth -a core /path/to/FluidR3_GM.sf2 output.mid
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```
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## See Also
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- Drum reference: `/drum_reference.md` in this skill directory
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