Yamaha DTXpress/DTXplorer/DTXtreme

You must use the two layers under the voice menu. First choose a pad. Then
choose the first sound you want. Then select the second layer, just put a 2
next to "V=".(you can change of layer in the first screen of the voice menu,
for example). Then make your settings for each layer(volume, pitch,
reverb,...). The X fade function will help you to have more dynamic.
Change the cross fade settings and hit the pad. According to the strength,
one of the two layers will be trig.