pi-agent
f19e3f0633
- 01-basic-chord.py: chord progressions (C major) - 02-90s-dance-track.py: 5-track 90s dance (arp, bass, pads, drums, piano) - 03-arpeggiator.py: reusable arpeggio generator with dir/type options - 04-single-note.py: minimal single-note example - Rewrite compose_neon_dreams.py: cleaner track functions, proper velocity=0 note_off, tick helper - Add README.md with setup and API reference Uses MIDIUtil library (beats-based API) instead of mido (clocks-based API)
120 lines
3.8 KiB
Python
120 lines
3.8 KiB
Python
#!/usr/bin/env python3
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"""
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03-arpeggiator.py - MIDIUtil arpeggiator
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Generates automatic ascending/descending arpeggios from chord sets.
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Shows clean patterns using MIDIUtil's beat-based time API.
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"""
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from midiutil import MIDIFile
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# ==============================
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# Configuration
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# ==============================
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BPM = 132
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PPQ = 960
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# Chord definitions: (root MIDI note, number of beats)
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# Using A minor progression: Am | F | G | E
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CHORDS = [
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{"root": 57, "beats": 4}, # Am (A3)
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{"root": 53, "beats": 4}, # F (F3)
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{"root": 55, "beats": 4}, # G (G3)
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{"root": 52, "beats": 4}, # E (E3)
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]
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# Arpeggio patterns: semitone intervals from chord root
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CHORD_TYPES = {
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"major": [0, 4, 7, 12], # Major triad + octave
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"minor": [0, 3, 7, 12], # Minor triad + octave
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"dim": [0, 3, 6, 9], # Diminished
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"aug": [0, 4, 8, 12], # Augmented
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}
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# ==============================
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# Helper function
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# ==============================
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def make_arpeggio(midi, track, channel, chord_list,
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arp_type="minor", arp_direction="up",
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subdivisions=4, volume=90):
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"""
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Generate an arpeggio track from a chord list.
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Args:
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midi: MIDIFile object
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track: track index (int)
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channel: MIDI channel (int, 0-15)
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chord_list: list of {"root": M, "beats": N} with MIDI root notes
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arp_type: chord type key for CHORD_TYPES dict ("minor", "major", etc.)
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arp_direction: "up" or "down" for arpeggio direction
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subdivisions: 16th-note speed (4 = standard 16ths, 8 = 32nds)
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volume: note velocity (0-127)
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"""
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notes = CHORD_TYPES[arp_type].copy()
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if arp_direction == "down":
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notes = notes[::-1]
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note_beats = 1.0 / subdivisions # duration per arpeggio hit
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beat = 0.0
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for chord in chord_list:
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root = chord["root"]
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chord_duration = chord["beats"]
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total_hits = int(chord_duration / note_beats)
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for i in range(total_hits):
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note_idx = i % len(notes)
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octave = i // len(notes)
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pitch = root + notes[note_idx] + (octave * 12)
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# Cap MIDI pitch range
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pitch = max(0, min(127, pitch))
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midi.addNote(track, channel, pitch, beat, note_beats, volume)
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beat += note_beats
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# ==============================
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# Create multi-track file
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# ==============================
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midi = MIDIFile(3, file_format=1, ticks_per_quarternote=PPQ)
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midi.addTempo(0, 0, BPM)
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midi.addTrackName(0, 0, "Arpeggio Lead 1 (Minor)")
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midi.addTrackName(1, 0, "Arpeggio Lead 2 (Major)")
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midi.addTrackName(2, 0, "Bass")
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# Track 0: Upward minor arpeggio (GM 80 - Lead 1 Synth)
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midi.addProgramChange(0, 0, 0, 80)
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make_arpeggio(midi, 0, 0, CHORDS,
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arp_type="minor", arp_direction="up",
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subdivisions=4, volume=85)
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# Track 1: Descending major arpeggio (GM 84 - Lead 3 Synth)
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midi.addProgramChange(1, 0, 0, 84)
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make_arpeggio(midi, 1, 0, CHORDS,
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arp_type="major", arp_direction="down",
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subdivisions=8, volume=80)
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# Track 2: Bass follows chord roots (quarter notes)
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midi.addProgramChange(2, 0, 0, 37) # Synth Bass 1
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for chord in CHORDS:
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root = chord["root"]
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chord_duration = chord["beats"]
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# Two quarter-note pulses per beat
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for beat_offset in range(0, int(chord_duration * 2)):
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time = beat_offset * 0.5
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midi.addNote(2, 0, root, time, 0.4, 100)
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# Octave pulse for depth
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octave = root + 12
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if octave <= 127:
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midi.addNote(2, 0, octave, time, 0.2, 80)
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# ==============================
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# Write to Disk
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# ==============================
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with open("arpeggiator.mid", "wb") as output_file:
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midi.writeFile(output_file)
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print("Written: arpeggiator.mid")
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print(" 3-track arpeggio piece with minor/major contrast")
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