-- lastValue
let x = mouseX kr 100 400 Linear 0.1
in sinOsc ar (lastValue x 40) 0 * 0.1

-- lastValue ; difference between currrent and the last changed
let x = mouseX kr 0.1 4 Linear 0.1
    f = abs (lastValue x 0.5 - x) * 400 + 200
in sinOsc ar f 0 * 0.2