Some press talk about it, and some years ago an English newspaper "Classic CD" spread a recording of socalled "Valse minute" played by Chopin in Nohant, apparently in 1848. The recording was bring to Pierre Boulez's IRCAM center in Paris from Jean-Michel Baillat, and here they discover it's a fake.
Instead you can hear the audio of Brahms also on You Tube.
And you can also see this wonderful site: http://www-ccrma.stanford.edu/~brg/brahms2.html
After all the first seems to me autentic, but not the second one.
Best regards,
Ben