Do you know the name of this documentary about music?

[molinarimusician]

I need to find a BBC documentary about classical music (or opera) that I have seen long time ago. I don't remember the name. I just remember a scene where the male host play and sing at the piano while reading a score, and then he tells that a conductor that doesn't know how to do that is not capable of interpreting anything. I have seen this documentary on Arte1 channel or People+arts.