if you want to keep your old spitfire main menu music back up the files go to DCS World/Mods/aircraft/SpitfireLFMkIX/Skins/1/EditorMusic and back up the files.
INSTALL: Go to DCS World/Mods/aircraft/SpitfireLFMkIX/Skins/1/EditorMusic and replace it.
It will ask if you want to overwrite. Do so.
if you have any problems let me know in the comments.
:if you want to listen to the mod here is the link.
https://www.youtube.com/watch?v=zSzBYDNt5U8