Related Clues:

• Paul McCartney played it for the Beatles
• Grouper, e.g.
• Voice below baritone
• Bigmouth, for one
• Clef below middle C
• He hits low pitches
• Barbershop necessity?
• Source of low pitches?
• Wide-mouthed fish
• Barry White, notably
• It's deep
• Deep end?
• Low-voiced
• Low part
• Paul Robeson, e.g.