Thanks to you, I am now hooked on Archie's music. It sounds amazing, and I usually love the Nexus playlists. But just to let you know, that song in a YT video on your profile says the player is too small when you hit the Play button.
I think you can. But it takes lots of messing around with de-compiling the game's innards, then converting the sound files for the Mammoth into a MIDI or MP3. Then, you gotta record and overwrite the MIDI/MP3. Lastly you inject it back into the game's source. I did it once for RA2 when I made my own militant army (e.g., Cuba, France, etc.) that had me as it's "construction manager". You know, like EVA. But I lost the files a long time ago.
You could research it to do it yourself. I know it can be done.