What is the piece John Williams is performing in this (wonderful) documentary (he is visibly shown playing it at 3:19)? Is it an original John Williams composition or what?
It's Le grillon, the second of French composer Maurice Ravel's song cycle Histoires Naturelles. Le grillon is French for 'cricket' (as in the grasshopper-like insect rather than the game). The words that the woman is singing are from poems by Jules Renard.
Thank you, Damien! I admit that it is pretty cool to just see John Williams play music for his own sake rather than anyone else's.