The terms A-side and B-side refer to the two sides of 78 and 45 rpm gramophone (phonograph) records, whether singles or extended plays (EPs). The A-side usually featured the recording that the artist or the 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, The Beatles 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 notorious for recording throwaway songs, often on-the-spot instrumentals, that were so weak that no one would confuse them with the A-side. With this practice, Spector was assured that airplay was focused on the side he wanted to be the hit side. Contemporary pop charts such as Billboard's Hot 100 are based on radio play and digital downloads, which do not have “sides” so the terms are becoming antiquated.