[media type]=[audio] [Genre]=[Soundtrack] [Duration]=>540
Get at a list of all your audio files.
Copy the code above and paste it into your MC search bar.
Job done. (at its most simple and basic level, it answers your question.)
There are many different ways you could arrive at this that might offer you more flexibility with regard to, selecting genres, for example.
Imagine a panes view that only lists tracks longer than nine minutes coupled with, at least, a "Genre" pane. The "Genre" pane would be automatically limited to only those values represented by the files in the list. Selecting "Soundtrack" gives the files you were looking for... Select a different genre, and, you see what I mean? The "more than nine minutes" thing is already taken care of.
A primer for creating your own views can be found here:
https://yabb.jriver.com/interact/index.php?topic=68960.0-marko