Reverb and delay effects can be widened using MS or other stereo-enhancement techniques on the return channel

Applying stereo-widening processing (MS encoding, comb-filter widening, pitch-shift widening) to reverb and delay return channels rather than directly to dry signal chains is advantageous because: (1) any timbral artifacts from the widening processor affect only the wet signal, not the dry vocal or instrument; (2) mono-collapse of the return channel is less damaging because the reverb/delay is a supplementary element, and its loss in mono is often acceptable or even desirable in complex arrangements that need central clarity.

Examples

Add a polarity-inversion comb-filter widener to a reverb return: the reverb blooms wide in stereo but collapses partially in mono, clearing the center for the lead vocal.

Assessment

Explain why applying stereo widening to reverb return channels is safer than applying it directly to a dry vocal track. Describe the mono-compatibility benefit.