Sysex checksums are used in music device data, one can request or send sysex data both ways, Computer<->Device
Portions of data must have a sum counted for a generated 7-bit checksum to pass inside the device
Sysex 7-bit Checksum:
CSM = 128 - (sum Mod 128) And 127
' sum would be sum of selected bytes from document, not a count