monstrosity.js

$('.circle').mouseover(
    function() {
        var sound = $(this).attr('class').split(' ')[2].replace('piano', 'sound'); // this is a monstrosity
        sound.play();
    }
);

$('.circle').mouseout(
    function() {
        var sound = $(this).attr('class').split(' ')[2].replace('piano', 'sound'); // this is a monstrosity
        sound.pause();
        sound.currentTime = 0;
    }
);