An STMB file contains a definition of a partial timbre used by SynclavierX, a digital synthesizer program. It stores information about a partial timbre, which is a collection of sampled sounds in SynclavierX that are used to compose music. STMB files may be created by users or may come preloaded with SynclavierX.

You most likely will only encounter an STMB file if you use SynclavierX software. However, SynclavierX has been discontinued, making STMB files uncommon. NOTE: SynclavierX is a program that emulates the capabilities of a Synclavier digital synthesizer, which was a physical music workstation manufactured from the 1970s to the 1990s.