the.com/wall of sound

means A dense, layered recording technique that stacks multiple instruments playing similar parts simultaneously, creating a thick, reverberating sound meant to work on radios and jukeboxes as a single overwhelming wave.

from Coined for producer Phil Spector's studio method in the early 1960s, where he'd cram large ensembles — multiple guitars, pianos, drums, percussion — doubling and tripling the same lines, then drench it all in echo chamber reverb. He reportedly wanted a sound so dense it would translate powerfully through tinny mono speakers. The phrase stuck as shorthand for that maximalist production style, later echoed (sometimes explicitly invoked) by acts from Bruce Springsteen to the Jesus and Mary Chain.