Zeta Instrument Processor Interface (ZIPI) was a research project initiated by Zeta Instruments and UC Berkeley's CNMAT (Center for New Music and Audio Technologies). Introduced in 1994 in a series of publications in Computer Music Journal from MIT Press, ZIPI was intended as the next-generation transport protocol for digital musical instruments, designed with compliance to OSI model.
The draft working version of ZIPI was primarily aimed at addressing many limitations of MIDI (Musical Instrument Digital Interface). Unlike MIDI which uses a peer-to-peer serial port connection, ZIPI was designed to run over a star network with a hub in the center. This allowed for faster connection and disconnection, because there was no need to daisy-chain multiple devices. Ethernet 10Base-T was used at the physical layer, but the authors tried to distance themselves from physical implementation as much as possible.
There were proposals for querying device capabilities, patch names and other system and patch parameters, as well as uploading and downloading samples into device memory.
ZIPI used completely new event system and complex note addressing schemes. At the heart of the new protocol was Music Parameter Description Language seen as a direct replacement to MIDI events. MPDL used a three-level hierarchy of up to 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, which was 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.
Some MDPL messages were direct carryovers from MIDI, given more pronounceable names in order to avoid ambiguity, but most messages were new and were 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.
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