I credit Benson's The Improvisation of Musical Dialogue with being an ambitious undertaking. One difficulty posed by the attempt to understand all music making as a process of improvisation is the question of how exactly one defines improvisation. Some of the traditions Benson is most conversant with (classical and "classical" music) don't present themselves as traditions of improvisation, and practioners of these forms of music often explicitly say they are not improvising. This is just one of the areas where the difference between what musicians think and what the musicologist thinks are sharply at odds. In the area of jazz improvisation, for instance, Benson is rather more comfortable with Adorno's celebrated opinions on jazz than he is with Sam Rivers' description of his own musical process back in the heyday of his free jazz period. There is no thought on Benson's part of privileging the understandings of the music maker. I point this out because it bears on an issue I would like to dig into for a moment. How much spontaneity is there in an improvisation? How many strings come attached to musical freedom? (The metaphor is that of a puppet, not a violin. Just thought I'd point that out, perhaps to think about polysemy, or homonymy, as you prefer.) Benson views practice and tradition as strings that make music dance, yank it around and all that. He needs a definition of improvisation that is not too precise (remember, he lists some eleven major senses of improvisation with minor variations, but does not tackle free improvisation head on) because he is going to apply it broadly. At the same time, he seems to feel that he cannot account for genuinely free improvisation because that would tip the scales towards musical freedom in general, and then then he would have no purchase on the genres he's truly conversant with. One might then be led to consider whether "classical" and classical musics, with the exception of modern early music movements, really have all that much to do with improvisation. Well, it's not for me to decide whether the whole endeavor should be sent back to square one. I do see another option, which is to regard improvisation as never having certain degrees of freedom or unfreedom, but always being improvised in its relation to freedom. That is, what improvisation means is always decided concretely, freely, in the moment of music making. (The moment relates to a musical practice in no set way, but is simply an opening for improvisation. ) To really see this, I think, one would have to seriously attend to a particular practice of improvisatory music, to know the difference between free variation and variations on freedom that could fundamentally alter a musical practice. And in general one might have to allow for a negative improvisation, for dispensations of liberties that are not quite egalitarian, and for liberties that are meant to negate the liberties of improvisation. To study musical improvisation in general would then be a monumental undertaking, requiring many monographs, many tomes.
Anyway, strictly for educational purposes, here's Sam Rivers in a later incarnation rehearsing his big band: