An SIMG file is a disk image file saved in the proprietary Synclavier Disk Image (SIMG) format. It stores a collection of sounds used to compose music with SynclavierX, a digital synthesizer program. SIMG files are designed to be mounted by SynclavierX to allow users to access all their songs in one file without having to load multiple files.

You most likely will only encounter an SIMG file if you use SynclavierX software. However, SynclavierX has been discontinued and SIMG files are no longer used, making them 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.