// Envelope Follower Controlling Sine Oscillator
// (Amplitude Theremin), by PRC 2008
// Rectify the signal (make it positive), and
//   leaky-integrate that into a low pass filter.
// Map that extracted envelope to the pitch of a sine wave

adc => FullRect r => OnePole p => blackhole;
0.999 => p.pole;
SinOsc s => dac;

while (1)	{
    0.05 :: second => now;		// update every 50 ms
    100.0 + p.last()*1000 => s.freq;    // map it to a good frequency range
}