The phrase "Wall of Sound" was coined to describe the production style adopted by eclectic production wizard Phil Spector in the early-to-mid sixties. The "Wall of Sound" formula was roughly as follows:

Stage one: Standard arrangement, one guitar, one piano, one drum set, one bass, what have you.

Stage two: For every instrumental part, add four to seven identical instrumental parts by that same instrument, played simultaneously. Drums and piano inclusive. Apply to vocals if appropriate. Add plenty of bells and whistles (often literally), and horns are a must.

Stage three: Don't multi-track it. Play it live, and stick one mic in the middle of the mess you've created.

I suppose stage four must've been "Profit!" because the unusual result certainly earned the appeal of the public. "River Deep, Mountain High" by Ike and Tina Turner was arguably most representative of the "Wall of Sound" method. This is perhaps arguable because you can somewhat hear the lead in that song--many of the tracks recorded during this period of his work had such focus on background instrumentals that the hook was lost. Somehow, it all seemed to work anyway.