Also on that obituary page last week (for Anneliese Rothenberger I referenced in my last post) in the Guardian was that for Edoardo Sanguineti. My knowledge of Italian avant garde poets and playwrights is a bit limited but his name rang a bell and I read on. I got to the mention of Laborintus and light dawned! He had a long working relationship with Luciano Berio providing various libretti for him. Here's a video of part of one of those works Laborintus 2 completed in 1965, a wonderfully wild piece - do stay for the really unhinged bit from around 5' to the end!
Unfortunately no subtitles and some Italian might help! There's a recording of this on a short Harmonia Mundi release (at least there was when I bought it!)