MU series are YAMAHA's XG sound modules, which uses 16bit PCM synthesis engine called AWM2.
XG is the format they made to compete with Roland's GS - Sound Canvas modules.
Following Roland, YAMAHA omitted full synth editability from most XG modules.
However, there are exceptions.
DB50XG Soundblaster daughterboard is the first fully-editable XG module, and MU10 is its module version.
Later, SW60XG sound card was added.
YAMAHA MU10 (1996)
QS300 Workstation Synth has the same synthesis engine with editability and a little bit extended layering ability.
YAMAHA QS300 (1995)
I made a new MU10 full Voice editor for Emagic SoundDiver.
It will work with MU10, DB50XG, SW60XG and QS300.
Follow the links below for downloads and the sound examples made with it.