Related Clues:

• Piano trio member
• Grouper, e.g.
• Voice below baritone
• Bigmouth, for one
• Clef below middle C
• Member of the strings
• Morey Amsterdam's instrument
• He hits low pitches
• Barbershop necessity?
• Instrument played sitting down
• Source of low pitches?
• Wide-mouthed fish
• Barry White, notably
• It's deep
• Violin's kin