listener

noun4

1. •
   Someone who listens, especially to a speech or a broadcast.

   • […] she would set herself going, telling the most interminable stories, until the last listener was fast asleep[…] — 1904
2. •
   A function that runs in response to an event; an event handler.
3. •
   (slang) A person's ear.

   • Fancy Gazette, quoted in 1823, John Badcock, Slang, a Dictionary of the Turf, the Ring, the Chase, the Pit, of Bon-Ton, and the Varieties of Life Gas now planted his favourite hit under the left listener of his antagonist, which sent him to dorse.
4. •
   (formal) A musical anthology.