The terms A-side and B-side refer to the two sides of 78 and 45 rpm phonograph records, whether singles or extended plays (EPs). The A-side usually featured the recording that the artist, record producer, or the record company intended to receive the initial promotional effort and then receive radio airplay, hopefully, to become a "hit" record. The B-side (or "flip-side") is a secondary recording that has a history of its own: some artists, notably Elvis Presley, Little Richard, the Beatles, Chuck Berry, and Oasis, released B-sides that were considered as strong as the A-side and became hits in their own right. Creedence Clearwater Revival had hits, usually unintentionally, with both the B-sides of their A-side releases. Others took the opposite track: producer Phil Spector was in the habit of filling B-sides with on-the-spot instrumentals that no one would confuse with the A-side. With this practice, Spector was assured that airplay was focused on the side he wanted to be the hit side.