midinoteoncps is designed to simplify writing instruments that can be used interchangeably for either score or MIDI input, and to make it easier to adapt instruments originally written for score input to work with MIDI input.
In general, it should be possible to write instrument definitions that work identically with both scores and MIDI, including both MIDI files and real-time MIDI input, without using any conditional statements, and that take full advantage of MIDI voice messages.
Note that correlating Csound instruments with MIDI channel numbers is done using the massign opcode for real-time performance,. For file-driven performance, instrument numbers default to MIDI channel number + 1, but the defaults are overridden by any MIDI program change messages in the file.
xcps -- returns MIDI key translated to cycles per second during MIDI activation, remains unchanged otherwise.
xvelocity -- returns MIDI velocity during MIDI activation, remains unchanged otherwise.
If the instrument was activated by MIDI input, the opcode overwrites the values of xcps and xvelocity with the corresponding values from MIDI input. If the instrument was NOT activated by MIDI input, the values of xcps and xvelocity remain unchanged.
This enables score p-fields to receive MIDI input data during MIDI activation, and score values otherwise.
![]() | Adapting a score-activated Csound instrument. |
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To adapt an ordinary Csound instrument designed for score activation for score/MIDI interoperability:
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Here is an example of the midinoteoncps opcode. It uses the files midinoteoncps.orc and midinoteoncps.sco.
Example 1. Example of the midinoteoncps opcode.
/* midinoteoncps.orc */
; Initialize the global variables.
sr = 44100
kr = 4410
ksmps = 10
nchnls = 1
; Instrument #1.
instr 1
kcps init 0
kvelocity init 0
midinoteoncps kcps, kvelocity
; Display the cycles-per-second value when it changes.
printk2 kcps
endin
/* midinoteoncps.orc */
/* midinoteoncps.sco */
; Play Instrument #1 for ten seconds.
i 1 0 10
e
/* midinoteoncps.sco */
i1 261.62561 i1 440.00006