Jonas Kaufmann's next cd, Sehnsucht, already out in Germany, is entirely in German. His German singing is as good as it gets. If you listen to him talk here, you hear that he is clearly a tenor. Gee, I love him.
The interview I used to show here is removed.
They mention that he speaks 5 languages and ask him to sing something in Swiss German. He says he can't think of anything. They ask him if he could sing something, and he talks a long time about how much he has to warm up before singing as a way of getting out of it. He says he warms up in the morning just to make sure everything is working correctly.