Ear

In a crossword puzzle the answer for "musical ability," three letters, was "ear."  (Another day the clue was "musical talent "and the answer was supposed to be "chops," but "chops" is not talent at all but merely technical prowess!) So we call it ear because musicians know that hearing, listening is more important than producing the sound. We call the capacity to write in verse, in a poet, an ear as well. So we know that the poet hears the verse. The painter sees, she or he has an eye. The chef tastes better than other people, the perfumer has a better nose.