// BRF is a band-reject filter SqrOsc so => BRF f => dac; // set osc frequency 50 => so.freq; // set filter Q .25 => f.Q; // set gain .5 => f.gain; // infinite time-loop while( true ) { // sweep the cutoff 100 + Math.fabs(Math.sin(now/second)) * 5000 => f.freq; // advance time 5::ms => now; }