I was curious about this too. Thanks for your excellent info.

For the record, the piano pieces used in this film are Erik Satie's "Trois Gymnopedie" and "Trois Gnossiennes." I don't think Welles used all six pieces, but I know that he definitely used Gymnopedie No. 1 and Gnossienne No. 1. Lovely pieces, of course, and widely available. The best interpretations are surely those by pianist Aldo Ciccolini, who was responsible for rediscovering Satie and (I think) for the performance featured in The Immortal Story. Pick up EMI's 2-CD set of Satie's piano work by Ciccolini.

I have a Satie CD; when I get a chance I will go over it and get the titles of the specific pieces for you.
"Long live the Organization For The Organized!"