well, i don't really know if this will help you or not, but it cannot harm to take a look.
I have been trying to build a kind of MIDI Xilophone.
i am following the plans from here:http://www.jdeboi.com/portfolio/electronics.html
In that page you can also find the code she used for it.
I am really just starting with electronics and also this Xilophone project is really in the beggining (and it is my first!!
I have hooked up one of the Piezo Disks (plus all the 5v, ground, anal and digit pins) to try it out.
Once i got some reading on the Serial Monitor i started looking into some Serial to MIDI converter.
There on the link above there is also a link for S2Midi converter.
I have been trying it but i am not sure it is working properlly.
I manage to open Ableton Live and to get Midi In Signal, but still i cannot assign the piezo disk to any thing. The signal coming in is always changing each time i "press" the disk.
Sometimes it shows as PitchBend2, some as PitchBend6... it always changes (but it seems to be always some kind of pitch bend).
Can it be that it is because i have only ONE of the disks plugged in?
What is the "Digital MIDI" thing you talk about?
After the Serial do Midi converter do we still need something before the actual "music software"?