Duct tape sticks things together, can be used to make, like, origami, protect yourself from nuclear disasters (apparently), and...
Oh, wait, Synthfont? It takes a MIDI and some soundfont files (*.SF2) you specify, and it applies 'em to result in better-sounding music. Sometimes. In other words, it does what any soundfont-compatible sound card would do, it just has the benefit of a lack of a memory limit when you're loading the soundfonts (well, for the most part, anyway), and MP3 dumping. Just add some reverb, and it can sound quite convincing.