Simple ScriptProcessor example

Quick example to show a scriptprocessor being used to generate a square wave. The script processor uses a phase accumulating oscillator, incrementing a register by an amount related to the frequency slider, and filling a sample output buffer with +1 or -1 depending on whether the phase accumulator value is positive or negative. The output of the scriptprocessor is connected to a BiquadFilter with cutoff and resonance controls, and the output of the filter is connected to the destination.