Possible Clues:

• It's about a family finishing song in back bar acting out 'D-I-V-O-R-C-E'
• It's about a family finishing song in back bar acting out 'D-I-V-O-R-C-E '
• Splitting
• What Sedaka said was 'hard to do'
• Finishing school no longer giving good reception
• Putting an end to getting divorced
• Disbanding, and a literal hint to the hidden theme in 17-, 23- and 46-Across