Now, it didn't used to be that way. Back when this was Adapted Score, all you had to do was arrange previously-written work, or the songs within your original musical, into an instrumental score. Which, like, if that rule was still in place, the number of studios that would squeeze an extra nomination out of that would be nuts. Think of Into the Woods, Pitch Perfect, Les Miserables, Black Swan, True Grit - they all would have been nominated here, you know it. Though the fact that they couldn't open up this rule for La La Land, Sing Street, and Moana makes me wonder if anyone knows this rule exists anymore.
Anyway. The 1976 nominees included arrangements of Woody Guthrie songs; arrangements of Paul Williams songs; and Paul Williams. The folk hero took the prize...sort of:
Actually, it was Leonard Rosenman, his second Oscar in a row, as he points out, having won the previous year for Barry Lyndon; he would eventually be nominated for his original score for Cross Creek.
The nominees for Best Adapted Score: