“Schleifen” is “loops” in German. Tilman Baumgärtel has written a book (in German) about the history and aesthetics of loops. Here is a review of the book, of course, also in German 🙂
Mind you, this is not a book about livelooping, but about loops, repetitions, in music.
Tilman Baumgärtel: „Schleifen. Zur Geschichte und Ästhetik des Loops“. Kulturverlag Kadmos, Berlin 2015, 352 S.