Synthesis and Downloadable Sounds
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DirectMusic Producer itself, and most applications that use DirectMusic to play content, make use of the Microsoft Synthesizer to create sounds. This synthesizer, which is a software component, accepts input in the form of messages and creates output in the form of pulse code modulation (PCM) data. The output data is then fed through a series of software buffers, where it can be further modified by effects. Finally, the data is passed to the hardware for conversion to a sound wave.
To create sounds, the synthesizer needs information about the expected timbre of those sounds. This information is in the form of samples that conform to the Downloadable Sounds (DLS) Level 2 standard, created by the MIDI Manufacturers Association. A sample might represent the timbre of a particular musical instrument at a given pitch or within a range of pitches; it might represent a non-musical sound effect; or it might even consist of a complete musical phrase.
The synthesizer can modify samples according to supplied parameters, which include pitch and articulation settings. It can also draw on different wave samples for different pitches and velocities of the notes being played.
Before a segment can be played in an application, the samples associated with the segment must be downloaded to the synthesizer. Downloading includes both DLS instrument collections and other waves included in the segment as sound effects.
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