in Music, signifies a change in the order of the notes which form a chord, or in the parts that compose harmony, which happens by substituting in the bass, those sounds which ought to have been in the upper part; an operation not only rendered practicable, but greatly facilitated, by the resemblance which one note has to another in different octaves. Hence we derive the power of exchanging one octave for another, or substituting in the extremes those which ought to have occupied the middle station, and vice versa.