Related Clues:

• Feline rumble
• Low vibrating sound
• Satisfied Siamese's sound
• Sound made by a contented feline
• Tuned engine's sound
• Losing energy, more refined sound from pet
• "Meow" relative
• Cat's joyful sound
• Contented sound as pussy unwinds, really relaxed initially
• What to do when you don't know the words to a song
• Contented animal sound
• Wordlessly sing
• Sound from a cat that's "making biscuits," perhaps
• (Keep scratching my chin, human!)
• [Keep scritching my head]