SIZE_STEPS = [30, 50, 67, 80, 90, 100, 110, 120, 133, 150, 170, 200, 240, 300];

currSize = SIZE_STEPS.indexOf(100)

/** Changes the size of the lyrics and chords. */
function size(steps) {
    if (steps === 0) {
      currSize = SIZE_STEPS.indexOf(100);
    }
    currSize += steps;
    document.getElementById('wholeSongDiv').style.fontSize = SIZE_STEPS[currSize] + '%';
}