I’ve created an SF2 format SoundFont (compressing to SF3 is not worth it really) for use on RAM-constrained devices, such as the Raspberry Pi. It’s comprised of:

• the piano from Fluid (R3) Mono 2.315 (which is very slim, one twenty-fifth the size of a wonderful new piano in MS_General)
• monoified (left channel, panned to centre) Choir Aahs (to save another 2½ MB) from MuseScore_General 0.2 (expressive and regular, for SND support)
• the harpsichord from MuseScore_General 0.2

The result, a whopping 7.3 MiB, is enough for accompanied voice, therefore called “SATBkc” — SATB, Klavier (Pianoforte), Cembalo (Harpsichord). It’s published under the same MIT licence as its two constituent soundfonts.

Download the soundfont (not going to package it, it has limited use) as well as a test score (in v3 format, it tests Single Note Dynamics too) if desired. Discussion on the MuseScore forum for soundfonts, please. Also remember that the waveforms generated from the soundfonts are, most likely, derivative works, requiring reproduction of legal notices.

Combined with TimGM6mb, this gives you full GM but better sounds for some instruments in just 13 MiB HDD and RAM (both are uncompressed SF2). “Choir Aahs” still could be better, but they are not “Choir Aarghs” any more at least ☺ TimGM6mb is GPLv2-only though so not universally usable (YMMV).