This is a fascinating confluence of activity: The composers James Saunders and John Lely have begun a major project about prose scores (here) and Phil Ford of the Dial M for Musicology has been using text based exercises in his teaching and there's some interesting discussion about this at the blog (here) . Also, Frog Peak Music has recently placed Christian Wolff's very influential Prose Collection online (here) and, of course, there is Upload...Download...Perform, which is just chock full of textual/musical excitement (here).
Such text-based exercises or pieces or scores were central to the teaching (in music and extra-departmentally) of the extraordinary pianist and theorist Jon Barlow at my grad school, Wesleyan, with immediate connections to Cage, Wolff, Oliveros, Lucier, Young, Fluxus, but also to Barlow's other interests, which ran to Euclid, C.S. Pierce, Wittgenstein, Ives, Baseball, Blake, Faulkner, Joyce, and Stein. Barlow's student, Kenneth Maue, investigated the genre in the early 1970's and while Maue's work clearly began in an avant-garde or experimental musical context, it rapidly entered into pedagogical and therapeutic terrain. Indeed, the compositions/piece/exercises in Maue's book Water in the Lake (1979) were probably more widely used in the classroom, in group training for business, and in personal training of a more therapeutic nature.
It is increasingly fascinating to me how superficially similar text scores can be, but how different their intentions and results may be. Stockhausen's two collections of text scores are wildly different from Pauline Olivero's Sonic Meditations, while the more conceptual line — from Young and Cage through many of the Upload/Downloaders seems to address more absolutely musical issues than the social processes featured in scores by other composers.
I have tended to reserved the prose score as an efficient format for broader conceptual work, often as a kind of generalized sketch for a work which might receive more conventionally-notated specific realizations but I've recently been returning to the form for some very specific pieces that could not really have been notated otherwise, and several of my older prose score have had some very good performances, which is very encouraging.