Swapping L/R channels reveals whether an instrument is truly centred in a stereo recording

It can be hard to tell whether an instrument in a stereo ensemble recording is exactly centred, especially in imperfect monitoring. A quick test is a plug-in that swaps the left and right channels: if the instrument moves appreciably when you swap, it is not centred. When correcting an off-centre or comb-filtered stereo image, first check for an inadvertently polarity-flipped channel (visible by comparing waveforms), then address timing/phase — always judging the result by ear, since the tidiest visual match may not be the most mono-compatible.

Examples

A snare that jumps left-right when you swap the channels is off-centre; comparing the two waveforms then reveals whether one side was polarity-flipped during recording.

Assessment

Describe the channel-swap test for a centred stereo image and the order of checks when correcting a lop-sided stereo recording.