The Influence of Musical Context on Tempo Rubato

Different pieces of music offer different expressive possibilities. Even a single piece of music offers the possibility to be treated in several expressive ways see (Repp, 1998). How much of this variety of possible interpretations is exhibited in actual performances of the music? Do pianists make use of the different parameters of the piece to shape their performance? Do variety in performances and variety in musical parameters relate to each other? Previous studies stress the relation between timing variations and musical structure (see Clarke, 1985), but provide no clear answer to the freedom that is allowed within this regularity, especially when multiple structural descriptions play a role simultaneously. In an experiment the melody of Variations on an Original Theme (Op. 21, No. 1) by Brahms, is set in different musical contexts derived from the Theme. Three pianists are asked to perform the melody in the different settings from a score. They repeat each performance several times. The settings are 1) the melody without bar-lines, 2) the melody with bar-lines, 3) the counter-melody, 4) the melody with the counter-melody, 5) the melody with block chords, 6) the Theme. The Theme contains all material of previous settings (the melody, counter-melody and block chords). The settings are presented in a fixed order and the pianists do not know the pieces before hand. Analysis of the recorded performances shows that pianists change the onset timing of the melody with respect to the musical context in which the melody is presented. Aspects of the context are imbedded in the timing pattern in different ways; for example, the addition of chords often causes a lengthening of the melody notes with chords, and the addition of a counter-melody constrains the lengthening of a melodic ornament. The melody proves to be the primary expressive source, while chords and a counter melody are good second ones. Both the variety in timing patterns and the extent of tempo rubato appear to increase with increasing complex conditions.