switching loops a,b,c, in echoplex How?

[Kem McNair <KemMc@n-jcenter.com>]

Hi. Folks 
Ive Got an echoplex dig. pro with 16 meg of ram in it. and have been
writing killer loops with multi,layers of drums ,guitar,bass & 
effects.  Now I need to do multi.layer loops, a,b,and c of a tune. then
be able to change to a,b or c after there written, on the fly  and lay
the parts to tape. Is this possible? If so, a step by step
explanation would be greatly appreciated. Boy It would be nice if
oberheim would put a SCSI port on the back of the echoplex  to save and
load loop samples to a hard drive.  That would be really useful
in live performance. 
Thanks for the input
KemMc@aol.com