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A command to draw only those parts of a Sound where a condition holds.

The following script draws all amplitudes larger than one in red.
   Create Sound from formula: "s", "Mono", 0, 1, 2000, ~ 1.8*sin(2*pi*5*x)+randomGauss(0,0.1)
   Colour: "Red"
   Draw where: 0, 0, -2, 2, "no", "Curve", ~ abs(self)>1
   Colour: "Black"
   Draw where: 0, 0, -2, 2, "yes", "Curve", ~ not (abs(self)>1)

Draw the second half of a sound:
   Draw where: 0, 0, -1, 1, "no", "Curve", ~ x > xmin + (xmax - xmin) / 2
Draw only positive amplitudes:
   Draw where: 0, 0, -1, 1, "no", "Curve", ~ self > 0
Draw parts where pitch is larger than 300 Hz in red:
   s = selected ("Sound")
   p = To Pitch: 0, 75, 600
   pt = Down to PitchTier
   selectObject: s
   Colour: ~ Red
   Draw where: 0, 0, -1, 1, "yes", "Curve", ~ object (pt, x) > 300
   Colour: ~ Black
   Draw where: 0, 0, -1, 1, "yes", "Curve", ~ not (object (pt, x) > 300)
© djmw 20170829