You might find files ending in .sf3 (compressed) or .sfz (text-based). Most modern players handle .sf2 and .sfz, but .sf3 is primarily used by MuseScore.
: They serve as "cheap, lightweight starter sounds" that can be heavily manipulated with modern effects for unique sound design. Modern Tools to Use Them old+soundfonts+work
Technical Report: The Functional Longevity and Modern Utility of Legacy SoundFonts (.SF2) You might find files ending in