Ok… now seriously, what the f… is Efim doing when he starts playing random notes on the piano and singing them like he knows what he’s doing? Diana is indeed into music and she knows what she’s doing, but we have to recognize that Efim is only doing some kind of dilly dally. He should stick to his cello and practice more, because his tempo is not good and his playing is lousy. In fact, what he should do is buy an electric bass and learn how to play it. It`s easier and he will se better results in a short period.
This is only my opinion and I don’t want to offend Efim, which on the other hand seems to be a nice guy. Let harmony and the classical music stuff to Diana and have fun playing blues with you f…. bass.