Classic Organ Works CMK-1, User Manual

Page: 22 / 105

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CMK-1 Manual (Issue-1)
Page-22
October 20, 2004
CLASSIC MIDI KEYBOARD
CMK-1
MIDI SPECIFICATION
MIDI ( M usic I nstrument D igital I nterface) is a communication system between computer-controlled music
instruments and describes all the actions of a musical performance. It was originally developed for music synthesizers
but, a few years ago, organ-builders began adding MIDI capabilities to pipe organs. However, as MIDI was not
designed for a complex musical instrument such as the organ, its standards are subject to organ-builders preferences.
MIDI is composed of three components which are the language (protocol), hardware (MIDI connector), and
distribution format (MIDI file)
[1] . The MIDI language is in binary format and is a uni-directional asynchronous
stream of bits at 31.25 Kbits per second with 10 bits transmitted per byte. The 10 bits per byte consist of a start bit, 8
data bits, and a stop bit. In the hardware domain, the MIDI 1.0 Specification (maintained by the MIDI Manufacturers
Association) recommends the 5-pin DIN 180° connector. The 5-pin DIN connector is standard and allows MIDI
equipment from differing manufacturers to be connected together. MIDI cables transmit information in a uni-
directional manner so connectors are designated as either input or output. MIDI files are the standard distribution
format. They capture all the details of MIDI onto a hardcopy medium. MIDI files are similar to the MIDI language
except that they add a time-stamp for each event so that MIDI equipment can replicate the timing required to generate
accurate performances.
[1] MIDI Message information can be found in Appendix B and Appendix C.
MIDI Sound Sets
General MIDI [2]
The MIDI Manufacturers Association (MMA) developed General MIDI (GM) to provide a standard relationship
between commands and sounds generated by synthesizers. A serious problem developed as the number of MIDI
device manufacturers grew. Every manufacturer associated different commands with different sounds. Users were
confused when they used a command to play a piano sound but ended up with some other instrument. To alleviate the
confusion, the MIDI Manufacturers Association dictated that commands termed ‘Patch numbers’ would be the
standard reference to a sound. A ‘Patch Map’ shows Patch numbers and their respective sounds. In addition, since
MIDI transmits using MIDI channels, every MIDI sequence begins by assigning a MIDI channel for each sound that is
transmitted. This assignment is termed ‘Program Change’.
In addition to standardizing the mapping of patch numbers to their respective sounds, the General MIDI protocol
defines a set of capabilities for General MIDI instruments. Included are a General MIDI Sound Set (patch map), a
General MIDI Percussion map (maps percussion sounds to note numbers), and a set of General MIDI performance
capabilities (number of voices, MIDI messages recognized, etc.).
MIDI channels 1-9 and 11-16 are used for chromatic instrument sounds, while MIDI channel 10 is used for ‘key-
based’ percussion sounds. Furthermore, the 128 program numbers are grouped into 16 related sets. For example,
program numbers 1-8 are for piano sounds, 25-32 are guitar sounds, etc. (a chart is shown on the next page). The pitch
of the sound is indicated by a note number. Note numbers on the ‘key-based’ percussion sounds of MIDI Channel 10
represent different percussion instruments. It should be noted that although sounds may have the same label, they may