Emu XL-7 & MP-7 User's Group

LSB - Least Significant Bit.  Used in Prgoram changes typically.
MSB - Most Significant Bit.  Ditto.
Data entry (like what data? dude?) -  Umm, hard to say out of context, but 
for us it's typically the rotating wheel used for scrolling.  On some 
synths it may be a slider, or knob.
sostenuto - Sustain.
variation - Hard to say out of context.  Where do you see it?
timber - The other part of a sound aside from pitch and duration.  Think 
of a filter as something that changes a tone's timbre.
NPRN - Non Registered Parameter Number.  How manufactures of midi gear get 
around being limited to only 127 MIDI CC's and such.
RPN - Registered Parameter Number.

rEalm