The album is an artificial construct, yet it is the main unit of organization for music. As its name suggests, it was originally a collection of separate records, in a sort of book that was similar to a photo album. (Doug Adams and I discussed the creation of the album in the very first episode of our podcast The Next Track.) For at least 70 years, the Album has dominated music sales and listening.
At the same time, the single has long been the gateway medium for discovering new artists, or for getting the latest songs by your favorite artist. This size of this record – 7 inches – was a sign of the more limited content it contained. But it also played faster, in part to fill up the record; a 7" record at 33 rpm would look half empty if it contained just one song per side. The single wasn’t only a 7" record: in Jamaica, 10" singles were common starting in the 1960s, and 12" singles started being released in the US in the early 1970s. (There were also double singles in gatefold sleeves; I recall a live set by The Cure that contained four songs on two 7" discs.)