Once the conceptual distinction between the three domains of musical reality has been understood and accepted, the process of music realization can be described schematically as in Fig. I. The essential information flow between the three domains is shown. The schematic illustrates that music realization is not a straightforward process but a complex mutual interaction of categorical (symbolic, or verbal), auditory, and acoustic representations of music. It is obvious that the process comprises, among others, the following psychophysical items:
- the technique of symbolic representation;
- visual and other non-auditory perception;
- auditory perception;
- learning and memorizing;
- evolution and application of theoretical concepts;
- motor control of the musical instrument;
- the physics of the musical instrument;
- the room acoustics involved in auditory feedback.
Although each of these psychophysical items on its own part stands for a number of complex problems which are by no means sufficiently understood as yet, the whole realization process i.e. composition and performance of music, obviously works quite well. This is due to the strong coupling between the three domains through feedback loops provided by the human sensory and motor organs. It is particularly this system of feedback loops which, on one hand, guarantees proper functioning of the whole system if used in its natural way, on the other hand makes scientific understanding of the process so difficult. From communication- and system-theory it is well known that almost nothing can be said about the functioning of a system composed of subsystems containing feedback loops, if the functional parameters of only one or the other subsystem are known. Rather, quite confusing conclusions about the function of the whole system may be drawn from such a limited knowledge. This probably is the ultimate reason why many (most?) musicians unconsciously prefer largely to ignore the psychophysics of what they are actually doing, rather than to attempt to operate on the basis of incomprehensive knowledge. They can hardly be blamed for that.
This cybernetic consideration of the realization process may also throw some light on the problem of finding the objective parameters which characterize the musical quality of a musical instrument. In Fig. I, the instrument is represented by the box ‚acoustical realization‘. Since it is just one part of a complex system containing several feedback loops, almost nothing can be said about the instrument’s musical value unless its physical parameters are considered in combination with all the other system parameters. However, while the physical parameters of a musical instrument can be determined quite precisely, several other parts of the whole system have been explored only to a limited extent as yet. A lot of experimental and theoretical research remains to be done. Fortunately, as already mentioned, the whole process, i.e. the conventional way of composing and performing music, works quite well, in spite of considerable gaps in our psychophysical insight. This is no longer true, however, when the use of computers in music realization is considered.