He puzzled out (and only later learned that 19th-century German engineer Heinrich Helmholtz had gotten there before him) that when two tones are played simultaneously and loudly enough, they interact to spawn two new tones.
He puzzled out (and only later learned that 19th-century German physicist Hermann Helmholtz had gotten there before him) that when two tones are played simultaneously and loudly enough, they interact to create two new tones.