Try the following using hoch.github.io/canopy:

var osc = new OscillatorNode(context);
var f = new BiquadFilterNode(context, {type: "notch"});

osc.frequency.setValueAtTime(261.6, 0.0);
osc.connect(f).connect(context.destination);

osc.start();
osc.stop(0.06);

There's a funny sudden jump in output at time 0.06.  That seems wrong, but I'm not sure.