Related Clues:
- Run smoothly, as an engine
- Run well
- Sound of tires on the highway
- Machine sound
- Make music, in a way
- Sing, in a way
- Electronic noise
- Play a guitar idly
- Play idly, as guitars
- Monotonous sound
- Substitute for forgotten words
- Sing wordlessly
- Participate without the lyrics
- Sound system problem
- Theme, Part 2