In this part of the score, low-level and high-level control parameters are initialized. Only these parameters will be accessible from within the related Score File once this particular Instrument is instantiated.
To initialize a low-level control parameter only its range (maximum and minimum value) and default value must be specified. The specific synthesis engine shall be in charge of interpreting this low-level parameters and apply low-level transformations on the synthesis data accordingly. Although these parameters are not exclusive nor limited to a particular synthesis scheme they have only been implemented, as a proof of concept, to control an SMS-based synthesizer.
A high-level control parameter must also include its range and default value in its definition. But besides that, it must also specify the way it relates to low level parameters or to the timbre space location, a relation that is usually referred to as mapping function. A single high-level control parameter may influence any number of low-level parameters. For defining the high-to-low level mapping all standard formulas as well as the previously defined break-point-functions may be used.
MetriX includes a set of standard low-level and high-level control parameters but the list is dynamical and can be enhanced for a particular case.
In [Scaletti and Johnson, 1988] the authors argue that Music-N makes it very difficult to control things at a higher or lower level. With this separation between low and high-level parameters that can then be controlled from the score we are indeed giving a solution to this problem. It is also important to acknowledge that this clear separation between low and high-level parameters was somehow inspired by that in ZIPI (see section 2.6.2).