// BRF is a band-reject filterSqrOsc so => BRF f => dac; // set osc frequency50 => so.freq;// set filter Q.25 => f.Q;// set gain.5 => f.gain; // infinite time-loopwhile( true ){    // sweep the cutoff    100 + Math.fabs(Math.sin(now/second)) * 5000 => f.freq;    // advance time    5::ms => now;}