Yamaha DTXpress/DTXplorer/DTXtreme

I've looked and couldn't find the answer in the archives.  Perhaps it 
is obvious to everyone else.

In an dtxpress II, I'm having difficulty getting to the gm midi 
voices.  I've changed the default channel from 10 for a specific 
pad.  I then can change pitch via the note setting. However, I can 
only change the midi voice itself via setting different channels, so 
I only have 15 choices, not the 100 or so I'm looking for. How do I 
get to the others?  What am I missing?

FWIW, I need access to some of pitched percussion voices (chimes) 
that aren't in the normal selection of  voices in the dtxpress.

Any help is appreciated.

Galen