Global Musical Tempo Transformations using Case Based ... - OFAI

Expression and Musical Structure Firstly, expression is used to clarify
the musical structure (in the broad sense of the word: this includes metrical
structure, but also the phrasing of a musical piece, harmonic structure
etc.). The research by Sloboda mentioned above [110] showed the influence
of metrical structure on performances by having pianists perform the identical
sequences of notes, differing in the position of the bar lines. The pianists
varied their performances such that e.g. the notes at the beginning of measures
were played louder and more legato than other notes. Furthermore, he
observed that the more advance the performers were, the more they utilized
this kind of expression, and the better listener’s were able to transcribe the
performed music correctly. This is a clear indication that expression is used
to clarify metrical structure.
Phrase structure also has a salient effect on performance. Phrases were
found to start and end slow, and be faster in the middle [59] . Moreover,
Todd [116, 117] invented a model that predicts the level of rubato of a given
musical piece, given a hierarchical grouping structure of the piece. The predictions
of this model are similar to the rubato patterns in professional performances
of the piece. Gabrielsson [42] found that pianists performing Mozart’s
Piano Sonata K. 331, tended to lengthen note durations considerably at the
end of phrases. Similarly, he found the tones to be relatively loud in the
middle of the phrases and relatively soft at the beginning and end.
Another form of structure that influences performance is harmonic and
melodic tension. Harmonic and melodic tension are commonly defined by
reference to the circle of fifths (where the tension is low for notes or chords
that are close together on the circle of fifths and high for those that are
far apart) [77]. Palmer [90] calculated a positive correlation between note
lengthening and tension. Contrastingly, no correlation was found between
note intensity and tension. In the same article, Palmer showed that melodic
expectancy (the extent to which an implied continuation of a melody is actually
realized (see also section 3.5.1 on the Implication/Realization model)
did correlate positively with note intensity (unexpected notes were played
louder), but not with note lengthening. As an explanation of the fact that
the expression of tension-relaxation and melodic expectancy are realized in
unrelated ways, Palmer notes that the two phenomena manifest themselves
on different time scales; tension-relaxation is a phenomenon at the level of
phrases and sub phrases (that is, a large time scale), whereas melodic expectancy
is manifest from note to note, i.e. on a smaller time scale.
In a general survey of the relation between expression and musical structure,
Clarke [24] proposes the interesting view that expression is tied to
structure by a limited set of rules (like the rules proposed by Sundberg and
co-workers citeSundberg91a,Friberg91, see section 2.2.2). Hence, the diver-
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