A UGen that toggles like a flip-flop between zero and one upon receiving a
trigger. The flip-flop initially outputs zero and changes to one when the first
// mouse-button toggle
// make sure lag is zero, otherwise the output
// never falls back exactly to zero!
val tr = MouseButton.kr(lag = 0)
val ff = ToggleFF.kr(tr)
SinOsc.ar(ff.madd(400, 800)) * 0.1
a signal to trigger the flip-flop. a trigger occurs
when the signal changes from non-positive to positive.