Everyone agrees that one of the particular characteristics of the electronic musical instrument is that it is configurable, either in its hardware structure or in its software functioning or in both hardware and software. Exactly how configurable, of course, depends upon the user’s skill and knowledge, and, consequently, the level at which the user can and wants to configure the instrument. At one extreme of the configurability scale, an unsophisticated user could purchase an instrument as an off-the-shelf item, deciding only the sounds that it will play. At the other extreme, a sophisticated and technically adept user might write custom software before beginning to make a sound. Given a wide range of decisions that could be made, one particular question becomes important: What are the principles that govern the structure and functioning of a musical instrument and how do those principles apply to an electronic musical instrument?
Whether acoustic or electronic, whether made of wood or metal, a musical instrument, in general, has three parts: a performance device, a sound generator, and a link that connects the performance device to the sound generator. In a violin, for example, the performance device is the strings and bow, the sound generator is the sound box, and the link between them is the bridge. In an electronic musical instrument, the performance device can be any “controller”, the sound generator can be any sound-generating mechanism, and the link between them is defined in software as well as hardware.
The crucial difference between an acoustic and electronic instrument is that the performance device, sound generator, and link in an acoustic instrument are inseparable, while the components of an electronic musical instrument are independent modules that can be brought together in any configuration to function together as a system. The inseparability of the components of an acoustic instrument is due to their interdependent production of sound: the performance device of an acoustic instrument initiates a sound which is conveyed by the link as acoustic information to be resonated in the sound box. The performance device of an electronic musical instrument, on the other hand, does not initiate the sound: it sends controls via the link to the sound generator.