Related Clues:

• Famed operatic trio
• Pavarotti, Domingo and Carreras
• Low parts
• Low-key performers?
• Vocalists
• Male singers
• Male singers from Reston
• Male voices
• Male singers with high register
• Male singing voices
• They sound high enough for getting on for a dozen alternatives, perhaps (6)
• What sound like notes hit the high notes
• High church hymns, by the sound of them
• They sound high or come in tens
• Low-down types, by the sound of them