VGMTool is a program that allows tagging, optimization, and general cleanup of VGM files (but should now only be used for tagging). It was originally written by Maxim in Win32 C++.
2R5 by Maxim is the last reliable official version of VGMTool. NeoLogiX released an update, 2R6, with improved YM2612 and YM2151 optimization but the update itself was considered too buggy for general use. An update, known as VGMTool 3, is in development which intends to modernize the codebase and allow compilation on non-Windows systems.
As early as 2012 NeoLogiX announced plans to completely revamp VGMTool for modern systems with the goal of making the codebase easier to update and maintain than the original Win32-only VGMTool source. Though he released screenshots of work-in-progress to garner attention and has uploaded source code to it, development is not complete. Release date is currently unknown.