Bach wrote the chaconne originally for violin, as the last part of 5 movements that form the second partita. Busoni transcribed it for piano, keeping the structure and melody the same, but making it richer with the options the piano has to offer. The opening theme is only 4 measures long, and is continuously repeated throughout the piece in different forms (variations) – this is typical for a chaconne. The corresponding bass line accompaniment is extremely simple and consists of the four descending notes D – C – B♭ – A (go here for more information about the structure of the piece).
The entire piece is, in my opinion, of incredible beauty, but there is one moment that stands out: the point where Bach switches key, from D minor to D major. In the recording from Grimaud this is at 8:30. The sheet music (p. 12) has the indication ‘quasi Tromboni’ (like trombones) and ‘dolce’ (gentle). The music is so fragile, so tender. I think Grimaud’s fingers are trembling (8:39!), and sometimes I even think I hear her breath. The bass line is still the same, still these four descending notes, now D – C♯ – B – A. But the shift from minor to major key has changed the atmosphere completely. Feelings of resignation and sadness shift towards wonder, towards a new world with opportunities and chances.
Brahms said the following about the piece (for violin, not the Busoni transcription), in one of his letters to Clara Schumann (the wife of Robert Schumann),
“On one stave, for a small instrument, the man writes a whole world of the deepest thoughts and most powerful feelings. If I imagined that I could have created, even conceived the piece, I am quite certain that the excess of excitement and earth shattering experience would have driven me out of my mind.”
If you want to hear the original version for violin about which Brahms is writing, see for example the version of Perlman, with a nice introduction from BBC radio. Personally (but I am biased), I think the piano transcription is even more intense and richer than the original for violin. Another nice view on the piece is from violinist Joshua Bell who says in the following video:
‘A journey… something very powerful, amazing. Bach manages to take you through the entire range of human emotions. Through discovery, longing, joy, spirituality, resignation, redemption, and finally a triumph… It stimulates the mind and perhaps it imitates life itself.’
As a side note, Joshua Bell is also the man behind the well-known subway experiment, where he’s playing the Chaconne during rush-hour in a subway station, and he’s hardly noticed by anyone:
I hope you enjoy the music. Let me know what you think or feel about it.