[chuck-users] pulse width modulation

I'm trying to model the following in ChucK "OSC1, OSC2, and an LFO (Low Frequency Oscillator) Modulation: OSC1 produces a simple square wave tone, the pulsewidth of which is modulated with OSC2, and then amplitude modulated with the LFO oscillator." I think I understand the LFO amplitude modulation part, but I don't understand what pulse width modulation with osc2 means. SqrOsc osc1; SqrOsc osc2; SqrOsc lfo; Gain master; lfo => blackhole; osc1 => master; 220.0 => osc1.freq; 0.8 => osc1.gain; 20.0 => lfo.freq; 0.9 => lfo.gain; fun void updateAtSampleRate() { while (true) { ((lfo.last() + 1.0) / 2.0) * 0.8 => osc1.gain; 1::samp => now; } } master => dac; spork ~ updateAtSampleRate(); 2::second => now;