Voice exchange

In music, especially Schenkerian analysis, a voice exchange (German: Stimmtausch; also called voice interchange) is the repetition of a contrapuntal passage with the voices' parts exchanged; for instance, the melody of one part appears in a second part and vice versa. It differs from invertible counterpoint in that there is no octave displacement; therefore it always involves some voice crossing. If scored for equal instruments or voices, it may be indistinguishable from a repeat, although because a repeat does not appear in any of the parts, it may make the music more interesting for the musicians. It is a characteristic feature of rounds, although not usually called such.

Patterns of voice exchange are sometimes schematized using letters for melodic patterns. A double voice exchange has the pattern:

A triple exchange would thus be written:

The first use of the term "Stimmtausch" was in 1903-4 by an article by Friedrich Ludwig, while its English calque was first used in 1949 by Jacques Handschin. The term is also used, with a related but distinct meaning, in Schenkerian theory.

"When a piece is entirely conceived according to the system of Stimmtausch, it belongs to the rondellus type."

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 importance was not lost on theorists of the time, either, as Johannes de Garlandia gave an example, which he called "repetitio diverse vocis," and noted in "three- and four-part organa, and conductus, and in many other things."

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