Unedited and not tampered with.
This here is the unused extended version of the Felix The Cat theme that was performed by Ann Bennett that winded up being heavily associated with the character. Especially given the more well known short version being used for the animated TV series that debuted in syndication back in the late 50s.
I sourced this from the Ann Bennett SoundCloud page which has a bunch of additional recordings by the singer regardless if it's Felix related or not.
RIP Ann Bennett