Notes about the S1V file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The S1V file type is primarily associated with 'Yamaha EX-series Synthesizer' by Yamaha. A "voice" file handles the 256 voice data as a single file.