How to play multiple audio track of video simultaneously on VLC
Launch VLC with the following command line options:
vlc --sout-all --sout #display
All audio tracks in the file will play.
Source: https://forum.videolan.org/viewtopic.php?t=145140
If you're running windows, the default player (windows media player) mix all tracks by default, at least on Win8. I don't like WMP and I'm still using VLC but WMP does the job when you need it.