ex-lsystem-rhythm.py

#!/usr/bin/python

# test-plsys-rhythm:
# generates a rhythm line based on an l-system sprouting structure,
# output over MIDI.

# import important things from isobar namespace.
from isobar import *
from isobar.io.midi import *

import random
import time

# generate a set of pitches based on an l-system, with recursive depth 4.
# symbols:
#  N = generate note node
#  + = transpose up one semitone
#  - = transpose down one semitone
#  [ = enter recursive branch
#  ] = leave recursive branch
notes = PLSys("N+[+N+N--N+N]+N[++N]", depth=4)
notes = notes + 60

# use another l-system to generate time intervals.
# take absolute values so that intervals are always positive.
times = PLSys("[N+[NN]-N+N]+N-N+N", depth=3)
times = PAbs(PDiff(times)) * 0.25
# delay = PDelay(notes, times)

# ...and another l-system for amplitudes.
velocity = (PLSys("N+N[++N+N--N]-N[--N+N]") + PWhite(-4, 4)) * 8
velocity = PAbs(velocity)

timeline = Timeline(120)
timeline.sched({'note': notes, 'amp': velocity, 'dur': times})
timeline.run()