If I may pop in with a couple other ideas,
The knowledgeable Zuzu_Typ is very correct
I only wish to add a few more ideas for Video Editors (one free, two non-free) that I use (off and on, at times, to this day):
Avidemux
Corel's
VideoStudio
CyberLink's
PowerDirector
Avidemux is completely free. It is a very small video editor, similar to an older program called VirtualDub (if you've used that in the past), where you can change the Audio Tracks in and out, as you describe
VideoStudio is a very capable video editing program, but not free
PowerDirector is another very capable video editing program, but not free as well
The two non-free ones are, however, less expensive than other "Professional level versions" of video editors (they are similar to Sony's less-expensive Movie Studio or Adobe's less-expensive Premiere Elements)
These are just ideas of course, try a whole bunch of different applications and find one that
you prefer... Good luck with it!