Yes, VirtualDubMod can also add any audio track to an AVI.
I suggest to do as follow (actually I don’t know if there is a better way).
First of all, save a copy of the original file somewhere in your HDD (it’s safer ;))
Then open the AVI go to menu Video --> Direct stream copy
Go to menu Stream --> Streamlist. Select the audio stream, and then press the “Disable button”. In this way you have a video only file with no audio.
Press F7 (or go to menu “File” --> “Save as” and save the file (as I said previously this is a video only movie) on a folder (possibly a different folder to avoid confusion and to be sure to not loose the original file.
Then open again the original video, the one with the audio you want to modify, and go to menu Stream --> stream list and select the audio track. This time press the “Save WAV” button. This save the audio only on a folder in your HDD.
After you modified the WAV file with the audio editor, to insert it in the avi run virtualdubmod and load the video only file you saved previously (the one with no audio).
Then go again on the menu “Streams” --> Stream list. Press the “Add” button and search for the audio file you modified with the audio editor.
Finally, select again the option “Direct stream copy” both for audio and video, and save the file with a different name. If you worked correctly with the audio editor, there should be no asynchrony between audio and video strams