O is for Open

In the 1960s, perhaps a bit earlier, a lively conversation started about "opening up" musical form, or even more directly, about a formal genre marked by such an opening, an "open form." This might mean that the composer opens up the continuity of a work to the non-obvious sequences, or that additional choices are given to the performer with regard to the same, or perhaps listeners might engage the form of the work in ways other than the simply chronological.  Sometimes this would work out to something less than a real opening, just a denser but still finite network of possible paths through a work (and, in some cases (Stockhausen, Boulez), it turned out that those possible paths were much more constrained than advertised), other times the opening was so open that the specific identity of a work was called into question.  The discussion had high points (the comparison between Feldman's Intermission 6 and Stockhausen's Klavierstück XI was one of them) but just sort of faded. Maybe it would be useful now, particularly in view to the increased pressures on the traditional concert format and the possibilities of new and/or alternative performance and listening enviroments, to begin this conversation once again.