Yamaha DTXpress/DTXplorer/DTXtreme

hallo people from the group...
i bought my dtxpress last week and have some troubles to get 
my idea running...i wanted to do the following:as i play with my 
band kind of drum and bass sessions...i wanted to use the dtx to 
trigger drumloops as padsongs to my normal akusticdrumset...
so the idea was to keep a steady song in a fixed tempo running 
and to change inside of this song drumsets with padsongs..as i 
have to give out a midiclock for the keyboardplayer...
i started to play some loops into my computer to edit those 
there..and recorded those loops back into the dtx as songs...to 
this point it worked well. But when i started to put this song on a 
pad the dtx changed the voices and played 
pianosounds..so..something with the mididefinition of the 
drumset seems to fail...can someone help me with my 
problems?..and is there generally a chance to work my idea out 
on the dtx?
especially it would be interesting to know something about the 
midiflow and architecture in the dtx..the manual itself didn´t gave 
me a lot of informations...would be great to get some tips from 
you,...thank you very much ...peace michi