In my opinion, this is the most wonderful piece ever created. Since I am a classical guitarist, I first heard the guitar interpretation of this piece. It was arranged by the great Andres Segovia. Of course, it is one of the most difficult pieces to play on guitar and Segovia once said that nobody could master it until he gets 50 (although later several guitarists proved him wrong).
I found out it was a violin piece and is a part of Bach's Violin Partita, BWV 1004. I discovered more the depth of the music and I really am touched with its melody.
The piano arrangement by Busoni is generally good, but is a bit rough in some parts though.