In further sense, this is an appearance issue, as appearance also includes language things for me. So, the question is, what foreign language do you consider as sexy? I don't think it's required to know every word of it, or understand it, but what languages have a sexy tone, an eroticing timbre or erotic sound for you? I am pretty fluent in French, and I think it is sexy, though sometimes it sounds a bit funny. But overall, it's very smooth, nice vocals, not so many harsh consonants.