"Robbie was right in that there were some good reasons for overdubbing the whole thing. Richard wasn't singing well, Rick's bass was out of tune, and Robbie wanted to improve his guitar solos. Also, the horns were recorded completely out of balance and had to be redone in New York with arrangements Henry Glove and I put together."
January 1, 1970
https://en.wikiquote.org/wiki/The_Last_Waltz