• As singers, they get on swimmingly in a school (6)
• Cello's big brothers
• Choir members
• Choir section
• Choir voices
• Chorus section
• Chorus voices
• Deep voices
• Heavy strings
• Low parts
• Low strings
• Low voiced singers
• Low voices
• Low-key performers?
• Operatic villains, often
• Quarters of many quartets
• Quarters of quartets
• Quarters of some quartets
• Some barbershop quartet members
• Some barbershoppers
• Some choir voices
• Some guitars
• The back of the choir?