in Music, is derived from the Latin preposition in, and vertere, "to turn any thing a contrary way."

It signifies a change in the order of the notes which form a chord, or in the parts which compose harmony: which happens by substituting in the bass, those founds 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; whence we derive the power of exchanging one octave for another with so much propriety and success, or by substituting in the extremes those which ought to have occupied the middle station; and vice versa. See MUSIC.