midi-lab

name	midi-lab
description	Write playable MIDI for an advanced producer: chord progressions, basslines, drum patterns, melodies, arpeggios, stabs. Key/scale aware, theory-grounded. Use when the user asks to "write a chord progression", "make a bassline", "give me a drum pattern", "build a MIDI loop", or names key/tempo/genre. Outputs both a human-readable recipe and a real .mid file.

MIDI Lab

Defaults

• Tempo: ask, or infer from genre (124-128 house, 128-132 techno, 174 DnB, 140 trance/hard, 100 hip-hop)
• Key: ask. House defaults if starting fresh: A minor / F minor / G minor
• Length: 4 bars loop / 8 bars progression / 16 bars build
• Quantize 1/16; loosen to 1/32 + humanize for swung tech house

Always deliver two things

1. A human-readable recipe: table:

Bar	Beat	Note(s)	Velocity	Length	Notes

Velocity bands: 100-115 accents, 75-95 body, 50-70 ghosts. Flat velocity is the #1 thing that makes MIDI sound programmed.

2. An actual .mid file: save to ~/Music/Producer/midi/, descriptive name (tech_house_bassline_Am_126.mid). Use mido:

import mido, os
from mido import MidiFile, MidiTrack, Message, MetaMessage, bpm2tempo

mid = MidiFile(ticks_per_beat=480)
track = MidiTrack(); mid.tracks.append(track)
track.append(MetaMessage('set_tempo', tempo=bpm2tempo(126)))
track.append(MetaMessage('time_signature', numerator=4, denominator=4))

notes = [(0.0, 57, 110, 0.5), ...]  # (start_beat, pitch, vel, length_beats)
events = []
for s, p, v, l in notes:
    events.append((int(s*480), 'on', p, v))
    events.append((int((s+l)*480), 'off', p, v))
events.sort(key=lambda e: (e[0], 0 if e[1]=='on' else 1))
last = 0
for tick, kind, p, v in events:
    delta = tick - last; last = tick
    track.append(Message('note_on' if kind=='on' else 'note_off',
                         note=p, velocity=v if kind=='on' else 0, time=delta))

out_dir = os.path.expanduser('~/Music/Producer/midi'); os.makedirs(out_dir, exist_ok=True)
out_name = 'tech_house_bassline_Am_126.mid'
mid.save(os.path.join(out_dir, out_name))

Naming pattern: <genre>_<part>_<key>_<bpm>.mid.

Composition heuristics

Chord progressions

• Always-works: i-VI-III-VII, i-VII-VI-VII, ii-V-i (deep house)
• Voice as 7ths / 9ths, not triads. Drop the root and let bass hold it.
• Tight voice-leading (≤ 3 semitones between chord tones)

Basslines

• House: rolling 1/8 or 1/16, mostly root, octave jumps for movement, ghost notes 50-65
• Tech house: more syncopation, off-beat accents
• Check bass vs. kick: if they hit in the same 30 ms window, move bass 1/32 later or sidechain harder

Drums

• Don't write the obvious pattern unless asked
• Tech house: 16th shaker with sin-wave velocity, off-beat open hat ("tss"), perc on 3.5 of every other bar
• House clap = tight clap + reverbed clap pitched +1 ST

Melodies / leads

• 5-7 note set. Pentatonic + one passing tone.
• Repetition + one variation: A-A-A'-B
• Tension notes (b9, #11) on weak beats only

Humanize

• ±3 ms hats, ±1 ms kick (keep kick tight)
• ±10 velocity hats, ±20 ghosts

Live integration

If the Ableton MCP is connected:

1. After saving the .mid, offer to import directly via session-bridge (creates a new clip in the highlighted slot)
2. Or, generate the notes directly into the active clip without ever writing a file: ask which the user prefers

Connectors

• search_live_manual for Live 12 MIDI tools (Scale, Arpeggiator, Note Echo, Random, generative tools) before quoting parameters
• Spotify search + fetch_tracks if the user names a reference; pull tempo/key from audio features
• Ableton MCP for direct clip writing
• library-browser if the user wants the MIDI to match an instrument preset they already own

After

Drop the .mid link, then ask: "Variant: busier, sparser, different key, or a complementary chord layer? Or drop it into the active clip in Live?"