Lang 's mannerisms at the keyboard are the not the basis of his immaturity . Let him moon and moan and fall into the throes of ecstasy if that is what he feels . In the booklet accompanying their new recording of Chopin 's two piano concertos with the Vienna Philharmonic , Mehta , who has long championed Lang , says that he has watched the pianist practice and that even when Lang thinks no one is looking , he plays the same .