It was not easy getting midi via ALSA to work and still it's crappy.
I use these programs:
Jack audio connection kit
all these are from the standard Linux Mint repositorys
In Synaptic install these programs:
jackd, libjack0, qjackctl
fluidsynth, fluid-soundfont-GS, fluid-soundfont-GM
rosegarden, rosegarden-data, lilypond
This may take some time. Esp the soundfonts are 110+ Mb.
First start Jackcontrol and Q synth.
press the setup button in Jackcontrol
I filled it in like this:
Press OK and press the connect button:
When this is ready, it's time to configure Qsynth
In Qsynth you need to press the setup button and this menu appears:
You need to alter MIDI, Audio and soundfonts.
Here you need to add the installed soundfonts I mentioned above:
These softfonts should be in this order to get the most out of it.
The start Rosegarden and ignore any errors:
In the audio settings, JACK setup tab its important to have Rosegarden to start JACK if it's not already running.
Now try to start the JACK server by pressing start on the JACK panel. If it doesn't start, you have to adapt the JACK settings. I managed to get it working by trial and error.
Then start Qsynth and when that is running, start Rosegarden and load any midi file and lets play.
MIDI hardware synth setup
MIDI software synth setup
Official softsynth support
Howto jackCtl connections