I know this is an old post. But I am really interested for a guide how you did this.
I am currently trying to replace BGM XA files in Mega Man X4.
I extracted XA files from the disc. These XA files have layered/multi channels in it. Like your.
I've managed to extract these .XA files from BGM1_U.XA using QuickBMS.
Now I want to convert them to .wav and replace BGM1_U_6 with other music. How did you re-compile it in a multi channel .XA file?