.PLG File Extension

Plugin file used by Sibelius, a music notation application; adds new features to the software, such as MIDI transposition functions; must be installed while the program is closed, since plug-ins are loaded when the program starts.

Log file created by older versions of Visual Studio (and Visual C++), a software development IDE; contains an HTML page with project build information; can be used for generating reports of automated builds in which an email referencing the HTML page is sent to the developer.

You can turn off the generation of build log files in Visual Studio by selecting Tools → Options, choosing the Build tab, and unchecking the "Write Build Log (.plg)" option.