an additional audiotrack
 

how can I join an additional audio track?

I suppose by "join" you mean play an external audio file:
With a movie-file loaded...
rightclick > Load external audio file
(or [Shift]+[L])
:wink:
If you're referring to more audio streams inside a media file (e.g. a .divx container):
http://forum.bsplayer.com/attachment...choose_907.png
http://forum.bsplayer.com/attachment...ection_548.png

haha, yes, external audio file was exactly what I meant :) However, it still doesn't work. perhaps the problem is that it is a flac-format file..should I try to convert in into ac3?

I've never tried it with flac, but AC3 should work.
:wink:
By the way: did you already 'discover' the option "Auto load external audio"?
It's under (rightclick >) Options > Preferences > Audio
(If selected an audiofile having the same name and present in the same folder as the videofile will be loaded automatically as 'external audio'.)