// patch
SqrOsc i => LPF f => dac;
// gain
.1 => i.gain;
// freq
100 => i.freq;
// resonance
3 => f.Q;

float t;

// go!
while( true )
{
    // sweep
    200 + (Math.sin(t)+1)/2*3000 => f.freq;
    // increment
    .05 +=> t;
    // advance time
    10::ms => now;
}