extract/edit/merge audio track

[skatenglide]

i have a 2002 restored version of a 1927 pre synchronized dialogue movie. parts of the original were thought to be lost at the time of restoration. the video is avc. it has 2 audio tracks; 1- original music and 2 - analytical commentary, both are aac.

i have now found a 2010 restoration which includes some parts previously thought lost. about 1/2 hr more video. the video is mpeg-4 (xvid). it has one audio track of original music - ac-3.

i would like to try to incorporate the audio track with the analytical commentary from the 2002 version into the 2010 version, keeping selection of the 2 audio streams under the player control.

i think it will require that some synchronization be done because of the additional 30 min video.

i am a newbie at this. i would appreciate any suggestions as to a general approach, including tools needed for individual steps.

[skatenglide]

i failed to mention that 2002 version is in mkv container and 2010 is in avi.

[Baldrick]

Use multiplexers to separate and join the audio, for mkv use mkvtoolnix and avi virtualdubmod.

I'm not sure what you can use to resync easily it though. Maybe an audio editor like audacity or goldwave.

[skatenglide]

i've extracted the commentary audio track from the mkv container.

do i now have a choice of trying to join the audio track to the avi container or perhaps converting avi to mkv and then joining the audio track? why would one chose avi or mkv?