Control in music and audio programming contexts can take on many different forms. For example, this could include the control of low-level audio processing parameters to create a desired synthesis outcome, the control of music or note events in a music or compositional scheme, or the use of a digital music instrument to control a sound algorithm running on a computer or microprocessor. For such control schemes to be generally useful to a large number of people, they need to conform to some known communication protocol. Perhaps surprisingly, only a couple proposed protocols are widely accepted for musical communications.
