respectively), form a structural core of chords in any key.^25 Although unaccompanied
melodies do not have explicit harmony, they can have a strong implicit harmony based on
the principle of‘broken chords’, whereby chord tones occur successively (often with other
intervening pitches) rather than simultaneously.^30 Thus K0016 has a strong underlying
dominant-tonic harmonic organization (Figure 21.5), which can easily be perceived by
harmonizing this melody with additional tones (sound example 5).
Expression
‘Mechanical’performances of a melody (as in sound example 1, which was produced by a
computer) involve strict adherence to the relative time values of notes as indicated by the
musical score, and lack any amplitude variation. Human performances are never mech-
anical in this sense, but feature systematic variations in timing and amplitude, which help
communicate the structure of the music and the performer’s artistic and emotional inter-
pretation of it.^31 –^33 In addition, there are fluctuations in timing and amplitude due to the
limits of sensorimotor control. Listeners are quite sensitive to expressive variations. They
can easily distinguish an expressive performance from a mechanical one, and can grasp an
emotional valence intended by a performer.
Complexity
In listening to a melody a listener has intuitions concerning its structural complexity.
K0016, for example, is relatively simple (informally evidenced by the fact that it can be
learned by heart after one or two hearings). Recently, Eerola and North have proposed a
computational model of perceived melodic complexity, which successfully predicts data
from complexity-rating experiments^34 (Eerola and North, submitted). Their model suggests
that perceived complexity is related to the degree to which tonally stable pitches are empha-
sized and to the strength of a beat, among other factors.f
Meta-relations
In processing a melody a listener hears basic perceptual relations (such as grouping and
metre) as well as relations between these relations, that is, meta-relations.4,37For example,
the slight misalignment of grouping and beat at the onset of phrase 2 in K0016 adds rhythmic
energy to the melody (the presence of a note or notes before the first beat of a phrase
331Figure 21.5 Harmonization of K0016. The letters below the staff give the chords in the key of C major, while the
Roman numerals above the staff indicate chord functions (e.g. Itonic, IVsubdominant, Vdominant).
fIt is worth noting that perceived complexity has also been computationally modelled in sentence processing.35,36
Sentence complexity appears to be related to the number and distance of dependent syntactic heads in a sentence.
It would be instructive to contrast computational theories of complexity in the melodic and linguistic domains.