Sage Audio draws a clear line between two concepts that often get conflated: phase interference, which involves the relationship between multiple signals, and phase rotation, which concerns the orientation of peaks and troughs within a single signal.
The distinction matters most when dealing with asymmetrical waveforms - signals that lean more toward the positive or negative side. Some instruments, like trumpet, naturally produce this kind of imbalance due to how they emphasize compressions over rarefactions. It won't affect how the signal sounds on its own, but it can change how processors interact with it.
Correcting asymmetry through phase rotation realigns the waveform's orientation without altering its harmonic structure or frequency response - the audio sounds identical before and after. This is achieved using all-pass filters, which shift phase without touching frequency content. What changes is how peaks and troughs sit relative to the zero crossing, and that matters because processors like compressors or saturators will respond differently depending on how symmetrical that balance is.
Sage Audio points to iZotope RX's Phase Module as the go-to tool for this: it measures the asymmetry and rotates the phase accordingly, leaving everything the listener actually hears intact.