The Yamaha XG was a synthesizer class, developed in the 1990s.
It has appeared in many 'incarnations', including software versions that can be run on home computers (e.g. under Windows).
XG Manager is an editor for XG synthesizers.
It can control any hardware or software synthesizer implementing the XG protocol.
It also supports the QS300 synthesizer as implemented on the DB50XG daughterboard, the stand-alone MU10 module and the SW60XG ISA card.