First of all, Thierry, I would like to apologize for how I insulted you the other day. Everything went wrong that day, and I got angered very easily. I can't say I truly believe your claims, but I will not say that what you say is impossible. I'm just sick of the constant bragging on this forum, most of which is probably not even true.
Anyway, I'm glad you have found interest in this piece. It is, indeed, a wonderful piece. Sadly, Busoni could not appreciate it, dismissing it as "ugly music" after Sorabji had personally played it for him. However, it is nice to know that people are able to appreciate it nowadays, as it is a beautiful work. I prefer the 2nd Sonata, however, though it is quite a bit more dissonant.
If you liked this, and have not heard other Sorabji pieces, visit amazon.com and browse their Sorabji collection. Be sure to look into Fantasia Espanol, Le Jardin Parfume, and Gullistan.
Regards.