11.ex-lsystem-rhythm.py

#!/usr/bin/env python3

#------------------------------------------------------------------------
# isobar: ex-lsystem-rhythm
#
# Generates a rhythm line based on an L-system sprouting structure,
# sending output over MIDI.
#------------------------------------------------------------------------

from isobar import *
import logging

def main():
    #------------------------------------------------------------------------
    # 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 = PLSystem("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 = PLSystem("[N+[NN]-N+N]+N-N+N", depth=3)
    times = PAbs(PDiff(times)) * 0.25
    
    #------------------------------------------------------------------------
    # ...and another l-system for amplitudes.
    #------------------------------------------------------------------------
    velocity = (PLSystem("N+N[++N+N--N]-N[--N+N]") + PWhite(-4, 4)) * 8
    velocity = PAbs(velocity)
    
    timeline = Timeline(120)
    timeline.schedule({
        "note": notes,
        "amplitude": velocity,
        "duration": times
    })
    timeline.run()

if __name__ == "__main__":
    logging.basicConfig(level=logging.INFO, format="[%(asctime)s] %(message)s")
    main()