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"""
04-rms-tracing.py - Auto-wah effect.
The auto-wah effect (also know as "envelope following filter") is like a
wah-wah effect, but instead of being controlled by a pedal, it is the RMS
amplitude of the input sound which control it. The envelope follower (RMS)
is rescaled and used to change the frequency of a bandpass filter applied
to the source.
"""
from pyo import *
s = Server().boot()
MINFREQ = 250
MAXFREQ = 5000
# Play the drum lopp.
sf = SfPlayer("../snds/drumloop.wav", loop=True)
# Follow the amplitude envelope of the input sound.
follow = Follower(sf)
# Scale the amplitude envelope (0 -> 1) to the desired frequency
# range (MINFREQ -> MAXFREQ).
freq = Scale(follow, outmin=MINFREQ, outmax=MAXFREQ)
# Filter the signal with a band pass. Play with the Q to make the
# effect more or less present.
filter = ButBP(sf.mix(2), freq=freq, q=2).out()
s.gui(locals())
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