Pythagoras and the Ratios (tumblebook)

Pythagoras and his cousins want to win a music contest, but first they must figure out how to play their instruments in tune, something that's never been done before.

While trying to fix the problem, Pythagoras makes an important discovery--notes that sound pleasant together have a certain mathematical relationship. When Pythagoras applies this ratio to his cousins' pipes and lyres, the result is music to the ears.