Zeta Instrument Processor Interface - MPDL

MPDL

ZIPI used completely new message system and a complex note addressing scheme based on Music Parameter Description Language (MPDL) protocol, which was a direct replacement to MIDI events.

Instead of MIDI Channels, there were three-level address hierarchy of 63 Families consisting of 127 Instruments, each having 127 notes, resulting in up to 1,016,127 individual note addresses. Instruments in a Family could be assembled from different physical devices. This arrangement allowed fine per-note control of synthesis parameters, especially useful for non-standard scenarios such as MIDI wind controller or MIDI guitar controller.

For example, instant note-on capability could mask the deficiencies of note detection (tracking) in guitar MIDI systems, especially on lower strings. When triggered, the note would begin sounding as a noise or an arbitrary low note until the controller logic had tracked the actual pitch, which would be sent by a follow-up message without the need to retrigger the note. Conventionally, messages could also address a whole Instrument or an entire Family, as an equivalent to channel messages.

Some MDPL messages were direct carryovers from MIDI, given more pronounceable names in order to avoid ambiguity, but most messages were new and based on a very different, although innovative control logic. The resolution of message parameters could be any multiple of 8-bit, potentially extending 7-bit resolution typical of MIDI to 32 or more bits.

There were also some higher-level messages corresponding to advanced program parameters, such as modulation, envelopes and 3D spatialization of voices, as well as instrument-specific messages for guitar, wind, and drum controllers.