A system of compromises in the tuning of organs, pianofortes, and the like, whereby the tones generated with the vibrations of a ground tone are mutually modified and in part canceled, until their number reduced to the actual practicable scale of twelve tones to the octave. This scale, although in so far artificial, is yet closely suggestive of its origin in nature, and this system of tuning, although not mathematically true, yet satisfies the ear, while it has the convenience that the same twelve fixed tones answer for every key or scale, C/ becoming identical with D/, and so on.