Yamaha DTXpress/DTXplorer/DTXtreme

here is the explination of the EZ tune from their web page.

EZ Tune System Debut - 7/23/2005
Our new EZ-Tune system makes our entire line of mesh drums more 
compatible with any sound module or trigger to MIDI interface. EZ Tune 
will give you more time playing and less time reading manuals. The way 
we acheive this is by putting the controls in your hands, not in your 
module. The Patent Pending status allows for release in mid-summer 
2005. The EZ-Tune system will be available in 8"-22" Visual, 
ConcertCast, and AcousTech series SilenTech electronic drums and kits.
and
The EZ-Tune system allows external control over the head before the 
signal gets to the module, giving it a very fast and easy set-up.