These studies on the model of musical performance are interesting not only from a scientific point of view, but also
from an practical one, both in the field of automatic musical performance and in general in the multimedia systems.
This research was supported by Telecom Italia, under a research contract Cantieri Multimediali.
2. ARCHITECTURE OF THE MODEL
The researches we have been making (Canazza et al. 1997c) prove that the performance of a piece following a certain
expressive intention can be described observing which variations take place with reference to a neutral and a nominal
performance of the same piece. By nominal performance we mean the mechanic performance of the score where the
metrical durations (the score) are accurately observed and by neutral performance we mean a literal human
performance of the score without any expressive intention or stylistic choice.
The model presented is able to obtain an expressive intention, transforming a neutral performance both with reference
to the score and the acoustic signal itself. It must be underlined that our approach provides for the adoption of
hierarchical structures similar to the spoken language ones (words, phrases), in the musical language. Once these
structures are recognized, it is possible to modify the parameter of a group of notes (for example metronome or
intensity) following a certain curve. Such curve describes the characteristic of the musical gesture on the group of
notes. It is therefore convenient to describe (appropriately codified) the information about the neutral performance
and the nominal performance (i.e. the score), the variations to be applied on the expressive traits of the single note
(timing, intensity, timbre), the subdivisions of the piece into expressive units (words, semi-phrases, phrases)
characterized by curves that modify one or more parameters of the notes that constitute them.
To this aim, we propose a new representation of the score, where the fundamental components and parameters of a
musical piece are highlighted. Moreover it is provided with a number of controls on expressive parameters that allow
the model to operate on the piece. Later we shall refer to this new score as metascore.
Expressive intention
Musical
Expressiveness
Model
Nominal performance Post Processing
^ Post Processing
^ Instrument Synthesis
Neutral performance Metascore Family Method 0- Synthesis
Driver Driver aMIDI
Hierachical structure
Figure 1 Architecture of the model.
The metascore is a file where the information about both a nominal performance and a neutral performance are
codified. The parameters of the neutral performance are expressed as deviations from the nominal performance. The
performances are read by a MIDI file and transcribed in the metascore. From the parameters of the MIDI protocol,
the model computes new parameters that describe the attack, the intensity, the spectral characteristics and other
physical attributes of each note. Thus, the basic parameters of each note are immediately accessible. Each of these
parameters is expressed in perceptual scale, in which the unit represents the difference between two perceptual levels
(e.g. the difference betweenf and ff for loudness). These parameters are independent from the particular musical
instrument that will play the score. The importance of the notes in the piece can be specified by parameters such as
the accent and the elasticity. This last parameter takes in account that expressive deviations are not made to the same
extent in each note because the score sets technical and structural limits that prevent the musical phrase from being
distorted (De Poli et al. 1998). The metascore also requires, as input, a description of the hierarchical structure of the
piece (fig. 1). As already mentioned, we should not see the notes of a piece as units independent one from another:
each piece has its own structure where the notes gathers to form the words or phrases of a musical discourse. For
instance it is possible to set the metronome profile and the intensity on groups of notes following the division in
words, semi-phrases and phrases. At the phrase level it is possible to specify an adjective inspiring the performance.
With reference to the adjectives and considering other factors such as elasticity, the model computes the deviations
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