Mixman TRK (for “Track”) files are the building blocks in the Mixman Studio and Mixman Studio Pro, applications aimed at creating music by matching and mixing beats and loops. To facilitate tempo-matching, the Mixman TRK files contain “slices” internally (somewhat like ReCycle REX files). There are a lot of Mixman TRK files available, and owners of Mixman Studio or Studio Pro can also create their own Mixman TRK files.
Cubase VST allows you to import Mixman TRK files onto Audio Tracks, automatically matching their tempo to the current tempo in Cubase VST. Actually, the program doesn’t import the actual Mixman TRK files; instead a copy of the file is created and converted to a regular audio file, the tempo being matched automatically in the process. This audio file is then imported onto the Audio Track, as when using the regular “Import Audio File” function. This means that once you have imported the file, it will not follow any tempo changes you make in Cubase VST - should you want to change the tempo, you need to re-import the file.