---
name: 90s-midi-composer
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.
license: MIT
compatibility: Linux with Python3, mido library
---

# 90s MIDI Composer

Create authentic early-to-mid 90s-style MIDI music using Linux tools and Python + mido.

## Prerequisites

Install required tools (one-time setup, requires sudo):
```bash
sudo apt-get install -y fluidsynth fluid-soundfont-gm
pip3 install --break-system-packages mido
```

## The Tool: Python + Mido

Mido is a Python library for working with MIDI files. Key classes:
- `MidiFile(ticks_per_beat=480)` — MIDI file container
- `MidiTrack()` — list of Message objects (one per instrument)
- `Message('note_on', note=N, velocity=V, channel=C, time=T)` — start a note
- `Message('note_off', note=N, velocity=V, channel=C, time=T)` — stop a note
- `Message('program_change', program=N, channel=C, time=T)` — change instrument
- `Message('control_change', control=N, value=V, channel=C, time=T)` — CC control
- `MetaMessage('set_tempo', tempo=μs_per_beat, time=0)` — set tempo (μs/beat)

## Timing in Mido

Mido uses **relative** timing. Each message has `time` = ticks since the previous one.

```
ticks_per_beat = 480  (PPQ)
1 sixteenth-note = 120 ticks
1 eighth-note    = 240 ticks
1 quarter-note   = 480 ticks (1 beat)
1 bar (4/4)      = 1920 ticks (4 beats × 480)
```

### Absolute → Relative Conversion

Build events with absolute tick offsets, then convert:
```python
def rel(items):  # items = [(abs_tick, Message), ...]
    items.sort(key=lambda x: x[0])
    out, prev = [], 0
    for at, msg in items:
        msg.time = at - prev
        out.append(msg)
        prev = at
    return out
```

## Creating a Basic MIDI File

```python
from mido import MidiFile, MidiTrack, Message as M, MetaMessage

PPQ = 480          # pulses per quarter note (ticks/beat)
BPM = 128
TEMPO = 60_000_000 // BPM

mid = MidiFile(ticks_per_beat=PPQ)

# Track 0: Tempo
trk = MidiTrack()
trk.append(MetaMessage('set_tempo', tempo=TEMPO, time=0))
mid.tracks.append(trk)

# Track 1: Drums (channel 10 = 9)
drums = MidiTrack()
# ... add drum messages ...
mid.tracks.append(drums)

mid.save('output.mid')
```

## 90s Aesthetic Guide

### Essential GM Patches (General MIDI)

| Patch | Name              | 90s Role              |
|-------|-------------------|-----------------------|
| 1     | Acoustic Grand    | Piano / melodic       |
| 37    | Synth Bass 1      | Driving synth bass    |
| 59    | Brass Section     | Hits, accents         |
| 80    | Lead 1 Synth      | **Arpeggio lead**     |
| 88    | Pad 4 (Choir)     | Warm atmospheric pads |
| 49    | Strings           | Harmonic texture      |
| 16    | Electric Piano 1  | Rhodes-style          |

### GM Drum Set (Channel 10 = channel 9)

| Note | Voice              | Note | Voice              |
|------|--------------------|------|--------------------|
| 36   | **Kick 1**         | 38   | **Snare 1**        |
| 42   | **Hi-hat closed**  | 46   | Hi-hat open        |
| 49   | Crash cymbal       | 57   | Tambourine         |
| 51   | Ride cymbal        | 50   | Low bongo          |

### Classic 90s Dance Beat (120-140 BPM)

```
Kick on every quarter note (1, 2, 3, 4)
Snare on beats 2 & 4
Hi-hat on every eighth note
Open hi-hat on off-beats for groove
```

### 90s Chord Progressions

- **Am | F | G | E7** — vi-IV-V-I in C (the quintessential 90s pop progression)
- **C | G | Am | F** — I-V-vi-IV (the "axis of awesome")
- **Em | C | G | D** — vi-IV-I-V (melancholy 90s feel)
- **Am | C | G | E7** — i-III-VII-V (minor-key drama)

### Instrument Patterns

- **Arpeggio lead**: 16th-note chords cycling root-3rd-5th-octave, ascending and descending
- **Walking bass**: Quarter-note chord tone movement, alternating arpeggio directions
- **Pad chords**: 3-voice voicings, hold ~90% of bar for smooth crossfading
- **Piano melody**: Pentatonic or natural minor scale, sparse 4-note phrases per bar

### Effects (Control Changes)

- **Reverb**: CC91, value 40-80 (higher = more spacious hall)
- **Chorus**: CC93, value 50-90
- **Filter**: CC5 or CC74, value 40-127
- **Expression**: CC11, value 100-127

### Song Structure Template

```
Intro (4 bars)  — Pads only, dreamy and sparse
Verse (8 bars)  — Drums enter, bass + pads + arpeggio  (no piano)
Chorus (8 bars) — Full arrangement, piano melody joins
Bridge (4 bars) — Breakdown or key change
Final Chorus (8 bars) — Return, full energy
Outro (8 bars)  — Drums simplify, piano arpeggio fade
```

At 128 BPM: 40 bars ≈ 1.25 minutes. Example: 48 bars = 1.5 minutes.

### BPM Recommendations

| Genre              | Typical BPM |
|--------------------|-----------|
| 90s slow jam       | 80-100    |
| House / dance      | 120-130   |
| Trance / techno    | 130-150   |
| Drum & bass        | 170-180   |

## Playing MIDI Files

```bash
# With fluidsynth
fluidsynth -a alsa /usr/share/sounds/sf2/FluidR3_GM.sf2 output.mid

# On macOS
fluidsynth -a core /path/to/FluidR3_GM.sf2 output.mid
```

## See Also

- Drum reference: `/drum_reference.md` in this skill directory