 Director Sidney Lumet (qv) writes in his book "Making Movies"  about an argument between River Phoenix (qv) and writer  Naomi Foner (qv). A scene in the movie concerns the character  played by Phoenix being interrupted while practicing a classical  piano solo. In the script, when he is caught, he breaks into a jazz  riff to cover his "embarrassment" at being caught doing something  serious. Phoenix fought hard against this, feeling that his  character would never be embarrassed about working at the piano.  Lumet was so impressed by the point Phoenix made, he shot the scene  the way Phoenix wanted it.