03-exponential-ramp.py - Exponential portamento with rising and falling times.

The Port object is designed to lowpass filter an audio signal with different coefficients for rising and falling signals. A lowpass filter is a good and efficient way of creating an exponential ramp from a signal containing abrupt changes. The rising and falling coefficients are controlled in seconds.

from pyo import *

s = Server().boot()

# 2 seconds linear ramp starting at 0.0 and ending at 0.3.
amp = SigTo(value=0.3, time=2.0, init=0.0)

# Pick a new value four times per second.
pick = Choice([200, 250, 300, 350, 400], freq=4)

# Print the chosen frequency
pp = Print(pick, method=1, message="Frequency")

# Add an exponential portamento on an audio target and detune a second frequency.
# Sharp attack for rising notes and long release for falling notes.
freq = Port(pick, risetime=0.001, falltime=0.25, mul=[1, 1.005])
# Play with portamento times.

# Play a simple wave.
sig = RCOsc(freq, sharp=0.7, mul=amp).out()