On this Linux system, the MIDI keyboard is in /dev/dmmidi2 and when
I try "cat /dev/dmmidi2" I get characters on screen when pressing the
keys.
Hmm, interesting. Anyway, I think the raw midi device is in
/dev/snd/midiC*D* (but I'm not sure it's as easy to open and test)
Here is a command line whereby the system works with "noteon":
fluidsynth -v -a alsa -o synth.gain=3.0 -o synth.verbose=yes
/usr/share/sounds/sf2/FluidR3_GM.sf2
The easiest way is to use the alsa rawmidi driver. Find the card name by
looking at the /proc/asound/cards file - find the row corresponding to
the right sound card, and the label within brackets.
In my case it's "Piano", so then the options I need to add are:
" -m alsa_raw -o midi.alsa.device=hw:Piano"
(of course in your case replace "Piano" with your card name)