ABSTRACT
Discussion The above excerpts are written to sound equally satisfactory with either of the two voices as the upper, that is, in the versionsBAand^. These passages are written in double or invertible counter point.1 The technique of double counterpoint is widely used by composers. Without it, it would be far more difficult to com pose extended contrapuntal works, as one would constantly have to invent new accompanying material. The use of double counterpoint ensures a consistent the matic content and a contrapuntal relationship not achievable by other means. Composers often invent themes in pairs, with one theme intended to accompany the other at each occurrence. We will study this relationship later (as that of subject and countersubject). The use of double counterpoint also ensures that a theme will not always have to appear in the same voice, but can be freely interchanged betw een voices. Each voice must be capable of functioning as a con vincing bass line and must as always be a satisfying melodic line in itself. In any given work, the two versions (positions) may follow one another immediately, as they do in the music above, or the second (voice-exchanged) version may be placed at some later point in the work, usually transposed to some other key.
