Related Clues:

• What you can do if you don't know the words
• Low, droning sound
• Sing with one's mouth shut
• Boring voice
• Amp problem
• "Dinger" or "drum" starter
• U2 album "Rattle and ___"
• U2 album 'Rattle and ___'
• Work smoothly
• Accompany musically, maybe
• Indistinct murmur
• Motor noise
• Fridge sound
• Insect sound of doubt
• Sound of a bee