Wikipedia
WildMIDI
WildMIDI is a free open source software synthesizer which converts MIDI note data into an audio signal using GUS sound patches without need for a GUS patch-compatible soundcard. WildMIDI, whose aim is to be as small as possible and easily portable, started in December 2001, can act as a virtual MIDI device, capable of receiving MIDI data from any program and transforming it into audio on-the-fly. It is the standard MIDI renderer for the GStreamer framework.