The B-Side
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https://www.classic45s.com/why45s/bsides/index.html
"This page displays about 600 songs that were on the B side of 45 RPM records. Often referred to as "singles", many casual observers assume that 45s have only one song. Except for some promo 45s, however, that is simply not the case, and the B side of these "singles" is almost always worth seeking out. B sides were used to store other great songs by the artist, other sides of the artist's musical personality, and songs not included on the artist's albums. This list is restricted to B side songs that are on one of the "best-of" lists we maintain (Kev Roberts, Dave Marsh, Rolling Stone) or that earn one or two stars from Classic 45s. We are including mp3 "snippets" of some of the tunes, which you can listen to by clicking on the blue "play" button. In some cases, the B side was actually the hit, as radio programmers ignored the originally intended A side, and in others the B side was a secondary hit that received significant airplay, enough to "chart" on Billboard magazine's singles charts. But many are simply overlooked gems that you may want to seek out."
For example:
