File with a .SYX extension contains MIDI System Exclusive notifications s in raw format. They are used in communication of a computer with devices compliant with SysEx. Notifications compliant with the SysEx standard can be of different length, they start and end correspondingly with marked data baits – F0 and F7, in hexadecimal format.

An example of use of a device compliant with MIDI and SysEx is storing a backup copy of data package of a synthesiser connected to a computer – ultimately on its hard drive.