...s of making rapid contacts, so as to set matter vibrating, and causing it to generate musical tones. The knowledge that the pitch of tone depended upon the rapidity of vibration was well known to Pythagoras ; the generation of sound by motion is familiar in the vibration of strings and wires in the Aeolian harp, and the sound of the wind in a tube. The tuning-fork is so proportioned that it produces so...