Tuner

noun

1. A person who tunes a piano or organ.
2. A device, electronic or mechanical, that helps a person tune a musical instrument by showing the deviation of the played pitch from the desired pitch.
3. On a musical instrument, a peg or mechanical device that changes the tension, and hence pitch, of a string.
4. The component of an audio system that receives radio broadcasts.
5. One who sings or makes music.