pi-midi-zone/skills/90s-midi-composer/SKILL.md

name, description, license, compatibility

name	description	license	compatibility
90s-midi-composer	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.	MIT	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):

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:

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

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

# 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