I've been using Synthesia to play my MIDI instrument, as it allows for a nice visualization of the notes and many instruments. The problem is that this program is neither free nor very portable, so every time I need to change the computer I play with I would need to reinstall it. I'm not interested in the whole "play songs" thing.
I just need a program that makes the sound my instrument says, with the sound font I decide. Anything else is a plus.
I have been snooping around a lot, the keyword being "MIDI instrument", "MIDI synth" etc. But I've only got pricey music recording programs (not what I'm looking for), and many '98 style freeware websites. I'm now using Coolsoft virtualMIDIsynth, that does the sound but I can't manage to change instrument.