I was listening to a Carmen McRae/Cal Tjader album on Concord. She started singing “Besame Mucho” and it was evident from the first couple of lines that she did not speak, or understand, Spanish at all.
A quick perusal of the album jacket explained that she learned the song phonetically, in the studio the day of recording. It is one of my favorite versions, along with one by Joao Gilberto. Interestingly, though his native language was Portuguese, Gilberto also sang in French, Spanish and English, perhaps a few more. He did actually speak the languages however.