for the last couple of decades many bands have compiled their albums to be top-heavy - ie all the "hits" at the beginning...then they start to release singles from the top end of the album.
leppard released six tracks in the UK off hysteria - an 11 track album
whacko jacko released 5 off Off The Wall and * - yes 8 off Thriller - girl is mine, billie jean, beat it, wanna be startin something, say say say, thriller and PYT. i don't know how relevant this bollocks is - but when you consider queen - they generally released about four per album during the 80s.
queen's era wasn't like this....until the 80s it was only commonplace to release one single just prior to album release and another in the months after release to "perk" the sales. so i guess in most cases until at least 1979 it would be the first single off each.
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