Hi Robert,
The "Device ID" you may be referring to is probably the "Model ID" which refers to the value in the System Exclusive Messages supported by the specific family of synthesizers.
For example, the Super-JVs (JV-1010/1080/2080 and XP-30/50/60/80) is 6Ah, the A-series (A-70 and A-90) is 7Dh, etc.
This is the fourth byte in each sysex string.
Many GM/GS synths have a common Model ID so that the units can respond to the same Sysex Strings which control their internal settings.
* Roland & Cakewalk Resources and Roland Newsgroups:
http://www.lilchips.com *