As you can see I am a slacker blogger, but I will try to write more now (yeah, right).
I was reading Anthony Cornicello's blog about improvisation (yes, Anthony, I read your blog). Improvisation certainly has its place in music, and can be used very well - not only with jazz, also with classical (Bach and that Brandenburg concerto movement with only two chords, I forget which one at the moment, Liszt and his improvisations etc), More modern people - Stockhausen, Fluxus Ensemble, Glass (yes even him), Cage, Brown, and do on. If a composer chooses not to use it, however, doesn't make him an elitist know-it-all snob (Charles Wourenin discusses this idea of elitism in this interview at NewMusicBox, very interesting whether or not you like his music - listen to Wourinen's
interview here).
I have heard people use the phrase "the tyranny of the composer" because we don't allow improv. Would we say "tryanny of the author" because Kafka didn't leave blanks in his stories, inviting us to improvise on what he wrote?