This evening I just heard on a jukebox a track - linked above - I remember from decades back: the excellent Hocus Pocus by the Dutch progressive rock group Focus. It rather takes me back. As the Wikipedia page says:
It takes the form of a rondo, consisting of alternation between a powerful rock chord riff and varied solo "verses" (in the original all performed by Thijs van Leer) which include yodeling, organ playing, accordion, gibberish lyrics, flute riffs and whistling.
This description doesn't do justice to Mynheer van Leer's energetic and amusing performance; he reminds me of the great Kenny Everett. Although he's eaten all the pies since those days (haven't we all from that era?) it's great to see Focus are still going strong: see Focustheband.com.
My favourites from Focus in the past, apart from Hocus Pocus, are the reflective Janis, Sylvia (YouTube here), Moving Waves, and their very nice arrangement of the brass chorale in the middle of the Giuoco delle coppie segment of Bartók's Concerto for Orchestra:. The original version is here; the Focus version is here. Anyhow, Focus in its current incarnation continues to be brilliant.
Addendum: There are a number of accounts of Jan Akkerman's use of classical music in his work for Focus in the 1970s. See Focus on Focus: Jan Akkerman: the classical element 1, which notes the particular problems Focus had in getting rights from Bartók's estate for the quote from Concerto for Orchestra.
Focus weren't the only prog-rock group to use Bartók. For instance, Emerson, Lake & Palmer's track The Barbarian from their eponymous 1970 album is a rock take on Bartók's 1911 piano piece Allegro barbaro. In fact prog-rock was largely responsible for shaping my early taste in classical music, as EL & P provided tasters of a number of composers, and slightly non-mainstream ones at that: Bartók; Aaron Copland, whose Hoedown, from Rodeo, appears as Hoedown on Trilogy; Mussorgsky, whose Pictures at an Exhibition was adapted by EL & P almost in its entirety; and Janáček, whose 1926 Sinfonietta is the basis of EL & P's track Knife Edge.