Well, that trumps my suggestions from the Elvis Costello catalog (P.P.S. I L-O-V-E Y-O-U and I S-T-A-N-D A-C-C-U-S-E-D). How about longest single word? I’ll submit the Jam’s “‘A’ Bomb in Wardour Street”: A-P-O-C-A-L-Y-P-S-E.
The 25th Annual Putnam County Spelling Bee has “hasenpfeffer” (12) in Magic Foot, and “elanguescence” (13) and “weltanschauung” (14) in Second. Although “elanguescence” is more of a spoken line in the middle of the song.
There was a song in the early 70’s called Scrumpdillyicious. It had 2 versions. One was a generic version that did not make reference to Dairy Queen and did not spell out the word in the song (the kids sang S-C-R-U-M-P dillicious scrmpdilliious is a land for you and me). There was a second, commercial version that mentioned Dairy Queen and did spell out the entire word in the song. Both versions were released on a 45 single.