Very frustrating this. Figured out the last two clues and have both messages.
Spent ages searching for divine inspiration as to who the composer / musician could be. Finally spotted a possible option in the grid, but it's only 15 letters and presume I need at least 19 for the preamble to work, unless there's another thematic item as well. Carried on looking for something else. Can't see anything else. Back to option 1.
Now searching the Internet for something that shows the sheet music for best known work but seems to be several notes played at once and I'm not a musician so how does that convert into one cell per column? And how does 15 plus 10 cells equal 29.
Now have endgame taking much, much longer than gridfill, thrashing about looking up random stuff on the Web, very frustrating. Presume there's a wrinkle I haven't figured out yet to get the extra cells. All extremely frustrating.