Dmitryi Sizonenco sends word that he has released a .sf2 soundfont specifically tuned for use with classic games such as Doom, Heretic, etc. The soundfont is called Silverspring, and is about 60MB in size. He provided a link to a sample recorded using the soundfont, which is a recording of D_E2M1, "I Sawed the Demons". The soundfont itself can be downloaded from here. In case you do not have a Soundblaster Live or Audigy, or one of the several other sound cards that support the .sf2 format, the download comes with a small software MIDI synthesizer program that can use .sf2 soundfonts.