Nowadays the composers probably cannot even play the piano (they just do it all on the computer) However in previous eras, when being a musician was more about performing then about composing, or let us say that musicianship involved both virtuoso playing and composing, probably the composer played his works better.For instance, Liszt possibly played his works better than anyone else.Chopin, probably played his works better than anyone else (although he is on record that he though Liszt played better).Beethoven before deafness set in played his own works better than anyone else.I believe the same is true of Mozart, Bach, and Scarlatti.Some exceptions that come to mind are Haydn (his playing apparently was nothing to write home about), Ravel and Debussy (some loved hisplaying some thought it was dreadful), and Grieg.I think Rachmaninoff played his own works superbly well (he himself liked Horowitz better). the same with Prokofiev who was a superb pianist (but he might have neglected piano palying bit by bit as he got more involved into composition).And who is going to decide who plays better?A more interesting question seems to be: How much does the composer know about his own compositions? Is he the ultimate authority? How much liberty can an interpreter take when playing someone else's works (specially if the composer is still alive)?Best wishes,Bernhard