tune

A tune is a piece or part of music; a song or melody.

Example: Whistling a happy tune can chase the blues away.

If you tune a musical instrument you make it so it will play the right notes.

Example: You tune it by making the strings tighter or looser.

If you tune a radio you set the frequency to get a certain signal.

If you tune-in to a show, you watch it or listen to it.