A-side and B-side are the traditional terms for the sides of 78, 45, and 33 1/3 phonograph records. They may refer to singles, EPs or long-playing (LP) records. The A-side of these phonographs would usually feature the song that the artists, producers or record labels intended to be a radio "hit", while the B-side was intended for songs that were strong enough in their own right.

As music moved away from LPs over time, the names "A-side" and "B-side" still retained their meanings in music as a way to describe a song's type of content, although said songs do not actually have a "side".

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