default.sf2 is FluidR3 GS by Frank Wen, released under the MIT license.

    Copyright (c) 2000-2002, 2008 Frank Wen <getfrank@gmail.com>

    "I hereby release Fluid under the MIT license."

Bundled as the built-in "-default-" General-MIDI SoundFont for the InsTune
music engine so area music plays on any runtime, regardless of whether the
host JRE ships a default MIDI soundbank (most do not). Players can pick a
different installed SoundFont via Settings > Audio > SoundFont.

Note: this build is reduced to keep the client small (~3 MB) and it trims
some GM patches (pads, choir, strings) that InsTune's dynamic songs use, so
those lanes can sound thin or near-silent even when correctly playing. For
fuller, more audible dynamic music, install a larger General-MIDI bank (e.g.
GeneralUser GS, ~30 MB, also free) and select it from Settings > Audio >
SoundFont (issue #1022).
