Couldn't agree more, Brendan. I used the lyrics (which I got from a combination of trial and error and a lucky guess) to determine the discarded letters, which enabled me to fill the grid. I don't think I could have completed it the conventional way, i.e. getting the theme from the clues.
I think I've now placed the the pegs correctly. Before I had the tune starting promising but ending like something by Stockhausen.
Satisfying endgame but the gridfill was too much for my liking. I prefer the easy ones!