[4] Structured audio (SA) is a new way of creating music that is standardized in MPEG-4. It joins conventional methods of digitally encoding music: sampling the sound stream [top] or recording the physical input to an instrument controller [middle]. (In point of fact, SA also includes the latter type of synthesis, which is similar to methods employed with the music instrument digital interface [MIDI].)
In a more powerful form of SA [bottom], sound synthesis primitives, such as oscillators and filters, are assembled into networks to create specific sounds. The assembly Instructions and commands to drive the network--not the network output itself--are sent to the terminal.
(c) Copyright 1999, The Institute of Electrical and Electronics Engineers, Inc.