Move a stereo file’s position between the left and right speakers at a set rate, from a slow drift to a fast flutter.
Constant-power panning
A linear crossfade between two channels loses level as it passes through the centre: at the midpoint each channel is at half gain, and the combined power is lower than at either extreme. Autopan uses the same pan law as the Stereo Width tool instead, which scales each channel by cosine and sine of the pan angle so the sum of the squares stays constant. The sweep does not get quieter as it crosses the middle.
Rate and depth
Rate covers 0.05 Hz to 15 Hz on a log scale, so slow, musical settings get most of the slider’s travel. Depth sets how far the sweep reaches from the centre: at 100% it travels fully left and fully right, and lower values narrow the sweep symmetrically.
Shapes
Sine eases in and out of each side, which reads as a smooth drift.
Triangle moves at a constant rate between the two extremes, giving the sweep a sharper turn at each edge.
Square switches between hard left and hard right. The edges are rounded over about 1.5 ms to avoid a click, since a true step in a pan curve is audible as one.
Example: widening a static pad
Rate 0.2 Hz, depth 60%, sine.
A pad recorded dead centre gains slow, gentle motion without leaving the mix. Raising the rate past a few hertz turns the same setting into a fast tremolo-like flutter instead of a perceptible left-right movement, since the ear stops tracking position once the sweep outruns it.