TV show theme music

It would be great if there was a feature to add your own theme. PLEX doesn’t always download and tag the correct theme.

If this feature already exists I can’t find it someone please walk me through it.

For instance I downloaded Star Blazers (cartoon from late 70’s early 80’s) and the theme song keeps defaulting to the Japanese version.

https://support.plex.tv/articles/200220717-local-media-assets-tv-shows/