Hi Noel. I assume you are referring to recording rather than live performance. I think there are levels of distinction when working with improvisational artists. Inviting a group of experimental musicians to improv together in the studio could be, (with digital recording), more a means of gathering a wealth of original samples to then manipulate into something representative of your own ideals, in my mind that’s a little closer to plagiarising rather than collaborating. If the improvisation were not tampered with in any way, and was a true ‘live performance’ recording rather than edited and manipulated then I would take no issue with it. I personally prefer wrestling with composition without any hint of improv. To my mind this is much more daunting, particularly if you’re composing outside of more standard forms. In answer to your question I don’t believe this has anything to do with a sliding scale in ‘pop’. Perhaps each music genre has its own sliding scale of depth and ingenuity but they each serve a different purpose.