Stream Segregation and Perceived Syncopation: Analyzing the Rhythmic Effects of Implied Polyphony in Bach's Unaccompanied String Works

[1] In contemplating Bach's works for solo cello, Pablo Casals remarked, "It is fantastic to think that with one note after the other there can be melody, the central voices and the bass all together. A wonderful polyphony-and this is an invention of Bach. We have to give the proper expression to each voice" (Blum 1977, 143-144). And in reference to Bach's works for solo violin, Jaap Schroeder observed, "We should also realize that Bach often writes a single melodic line that has polyphonic implications which should be brought out in performance . . . Bach and Telemann knew that a single melodic line, as well as two juxtaposed melodic lines, could suggest polyphony and would be perceived as such by the listener if the player were skillful" (Schroeder 1977, 10-12).(1) The compositional technique to which they refer is typically called implied polyphony, compound melody, polyphonic melody, or pseudopolyphony. It is the perception of multiple voices or melodic lines within a strictly monophonic texture.[2] Most existing analytical approaches focus on identifying the underlying voice-leading patterns that are created by implied polyphony, both within and between implied voices. Fewer studies combine this analysis with an investigation of the degree to which these implied voices are perceived by listeners and emphasized by performers. After a brief survey of previous approaches, this paper presents an additional way to analyze implied polyphony and hear these pieces. Rather than focusing solely on harmony or voice-leading, this analysis is based on perceptual principles of auditory stream segregation and generates alternate interpretations of the number of implied voices and the content of each voice. This approach draws attention to the rhythmic effects of implied polyphony by highlighting how transitions from one implied voice to another create phenomenal accents that might otherwise not be present. In many instances, these implied voice changes generate a sense of syncopation by creating groupings of attacks at the fastest level of the metric hierarchy that are contrary to the accent patterns of the notated meter. This preserves a fundamental characteristic of Bach's metric structure that could be lost if the music is perceived as unrelentingly monophonic and isochronous.Earlier Approaches to Implied Polyphony[3] In the seventeenth and eighteenth centuries, implied polyphony was most often described as a way to transform a multi-voiced harmonic progression into a single melodic line through the use of arpeggiation. Among the many possible roots of this practice was the Baroque style brise ("broken style"), a technique that lute players often used to adapt the improvisatory style of thoroughbass accompaniment to their own solo instrumental repertoire. Since a lute is not capable of performing sustained tones, arpeggiation provided a way to play chordal passages that still had a sense of voice-leading. Performers of other instruments soon adopted this stylized form of arpeggiation, with the well-known Prelude in C Major from Book I of Bach's Das wohltemperierte Clavier providing a clear example of how a Baroque composer would write out the arpeggiations of a simple harmonic progression for performance on a keyboard instrument.[4] Various eighteenth-century theoretical treatises reflect a similar approach to explaining implied polyphony. Johann Mattheson (1739) called this technique the "theory of broken chords" and devoted an entire chapter of Der volkommene Capellmeister to illustrating the different ways that arpeggiation can be used to represent various polyphonic textures. To Mattheson, "breaking" meant that "the pitches are not perceived together all at once but one after another" (Harris 1981, 670). This technique was therefore a way of reducing the total number of voices while still retaining the full harmonic content. Johann Philipp Kirnberger (1774) discussed "Embellished or Florid Simple Counterpoint" in the eleventh chapter of Die Kunst des reinen Satzes in der Musik and demonstrated how arpeggiation could be used to transform various multi-part pieces into monophonic melodies. …