Voice exchange

Voice exchange appeared in the 12th-century repertory of the Saint Martial school as a consequence of imitation. Voice exchange first became common in the Notre Dame school, who used both double and triple exchanges in organa and conductus (in particular the wordless caudae). In fact, Richard Hoppin regarded voice exchange as "the basic device from which the Notre Dame composers evolved ways of organizing and integrating the simultaneous melodies of polyphony," and of considerable importance as a means of symmetry and design in polyphonic music as well as starting point for more complex contrapuntal devices. The elaborate patterns of voice exchange in pieces like "Sederunt" prove that Perotin composed them as a whole, not by successively adding voices. It also appears in the lower parts (pes) of "Sumer Is Icumen In", while the upper parts always include a new melodic phrase instead of a true voice exchange. Voice exchange gradually died out after 1300, due to the gradual separation of voice ranges and the expansion of the ambitus of a composition. In analyses, this is represented by two crossing lines with double arrowheads indicating the exchanged pitches. A common exchange of this sort involves a progression of a third using a passing tone, the exchange notated by the interval succession 10-8-6 (if this is with the bass, the third chord is a first inversion of the first). This is in effect a prolongation of the third (generally as part of a triad), a preservation of the harmony across a time span. Another type of exchange has the interval succession 10-10-6-6 (or 6-6-10-10) and involves a pair of notes exchanged across parts. ==See also==