QuickTime 3 Reference
The QuickTime music synthesizer component is a software-based synthesizer that is included with QuickTime. The sound it generates can be sent to the built-in speaker of a Macintosh or Mac OS-based computer or to the sound card or built-in audio circuitry of other computers.
The QuickTime music synthesizer includes a variety of built-in instruments in the atomic instrument format. You can also create new instruments for the synthesizer. The instruments used by the QuickTime music synthesizer are known as atomic instruments, because they are defined using QuickTime atoms.
The instruments of the QuickTime music synthesizer are described by a set of knobs, and one or more waveforms.
To play notes, you normally use the note allocator or tune player component. These components invoke the QuickTime music synthesizer or another music component to generate sounds. If you need to use the QuickTime music synthesizer directly, you must open an instance of the note allocator, which is responsible for finding the instrument components that best fit the criteria for instruments, and leave it open while using the synthesizer. If the note allocator is not open, the QuickTime music synthesizer may be forced to repeatedly open and close connections to the note allocator, which can greatly diminish performance. This recommendation may also apply to other music components that use the note allocator's instrument library routines.
Atomic instruments for the QuickTime Music Synthesizer are defined by some waveform data and a set of knob values. Knobs provide a way to modify the instrument sound--for example, by applying a tremolo. Typically, the instrument has a full list of knobs, and if the instrument contains more than a single sample, each sample contains values for several knobs that are tuned for that particular sample. In this context, a sample is defined as a short recording of a musical sound.
Knobs can be specified either by index or by ID. A nonzero value in the high byte of the 24-bit number field of an instrument knob record Instrument Knob Record or knobID field of a knob description record Knob Description Record indicates that it is an ID. The knob index ranges from 1 to the number of knobs; the ID is an arbitrary number. You should generally access knobs by ID, because knob IDs do not change over different versions of the QuickTime software whereas knob index values might.