Notes about the A21 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 A21 file type is primarily associated with 'Soundweb' by BSS Audio. Along with a .DIS file, a firmware update to networkable Soundweb digital signal processors.