Help on BOSS GT 100 MIDI

[Runner]

Hi, I'm new here,
I'm looking (since 2 years, when v.2.00 appeared) for some help on playing some keyboard sound with my guitar using the MIDI feature of the GT 100.
I tried a lot, with a Korg X3 and a Yamaha PSR 3000, but I can't have any sound.
Any suggestion?
Thanks a lot!

 

[rsm]

The guitar-to-MIDI signal is output over the USB or MIDI out connection; it's single notes (monophonic) only. It has to be turned on manually, IIRC.