Project file created by Cakewalk, an audio production application; may split the production across multiple tracks and can include MIDI data, references to audio files, fader settings, tempos, audio effects, and other settings.
The ".wrk" extension is used by older versions of Cakewalk. Newer versions use the .CWP extension.
Database backup file created by SQL Server, a relational database management system (RDBMS); saves a backup of transaction logs while they are being copied to secondary storage; renamed to ".trn" when the backup is complete.
The ".wrk" extension is assigned to the transaction log backup file temporarily during the backup operation. Therefore, if you see a WRK file that has not changed for a long period of time, it is possible that the backup operation failed.