Dear Sir: I´m sorry, I think that I´ve not been so clear. I´ll try to be more. Recently I saw a film with Isabelle Huppert, "The pianist". In that film she plays with other coleague (two pianos) in a private concert. And I wish to know what´s that work. If I understood it´s Bach.
I haven't seen the film, but as it happens I read a review of it a couple of days ago which said Schubert is the favourite composer of the character played by Isabelle Huppert. Schubert wrote quite a few pieces for two pianos and the piece you heard may have been one of those. Probably the most likely one is the Fantasia in F minor, which would fit pretty well with the general atmosphere of the film as described in the review! Happy hunting, and let us know how you got on.