Possible Clues:

• Many a pop group
• Maybe U2 appearing, as Irish broadcasters tense
• Two violins, viola and a cello string group
• Group that performs creative work interrupts formal meal, ignoring ban
• Players just outnumbering crowd?
• Barbershop group?
• The Beatles, e.g.
• Four persons of note
• Group of four musicians
• That's got four 31 acrosses