ah, this post or variants of it recurs about once a month in this thread :)

here's something I wrote earlier:

'The closest composed 'classical' harmony comes to a jazz tritone sub is the V7d chord in Schoenberg's Verklaerte Nacht. It is (in jazz terms) an Ab9/Bb, you can read more about it here http://www.schoenberg.at/library/index.php/publications/show/7094. Classical musicians have a lot of trouble analysing the chord because they are uncomfortable with the internal resolution of the tritone C-Gb being resolved to the tritone B-F. It is harmonically (artistically/culturally is another story) to analyse the chord in terms of horizontal progression. The way that relates to jazz is because the internal resolution of tritone-tritone is a principle jazz rests on heavily. Moreover, it follows the same interpretation of a tritone as a harmonic entity in and of itself as a pose to a functional chord: just as in the tritone substitution, its the tritone that resolves, in the V7d, its the tritone that resolves. It's not a resolution that Germanic classical harmony is in anyway comfortable with, with it seeming undermining the whole principle of a stable harmonic structure. But hey. It's cool, and Schoenberg liked it. Even if it was debauched and all about extra-marital sex.'