FluidSynth

FluidSynth is a software MIDI synthesizer, meaning it can convert MIDI input or files to audio and can be used to emulate a MIDI device or as a MIDI player. It supports the SoundFont2 format of digital audio samples for the MIDI instruments (it does not include a default one).

It supports outputting the audio in Linux to ALSA, Jack and OSS and emulating ALSA and OSS MIDI devices.