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

--Can a user do anything with the Riffs?  The manual lists them all, 
but can they be assigned to anything?  Or are they just there to 
audition the presets? I did read the comment suggesting recording 
them via MIDI in, but are there any other possibilities?  It seems 
strange to list them (and not the Arpeggiator patterns, for instance)
if they can't be used for anything or reassigned.
--And also, what are the actual functions of the Mod 1 & 2 knobs?  I 
don't think this is mentioned at all in the manual.  I know they can 
be assigned to whatever you like, but what is the default function?
--Another question: exactly what parameters does Randomize Preset 
randomize? Does it ever create patches with different Instruments on 
each layer, or is there a way to make it do so?
--BTW, I'm completely blown away by the functionality in this 
machine.  It's completely deceptive.  On the surface it appears to be 
a dance/techno box and nothing more.  But the features E-mu packed 
into it are on a par with modular systems.  Yeah, mine has frozen up 
on me a few times. But I still love it!