Xenakis. Kraanerg is (as far as I know) his longest composition at 74 minutes, and the only full-scale ballet in his ouevre. Composed in 1968 for the opening of the Ottawa National Arts Centre, the ballet as performed had no storyline and by most accounts wasn't up to scratch, but Xenakis was clear in the music's inspiration. The work's Greek name is a portmanteau word of his invention meaning 'energy of youth', with the dramatic sonic landscape taking its cues from the student protests of the time.
A combination of live orchestra and electronically-manipulated orchestra on tape, Kraanerg shifts between the two with increasing amounts of taped material dominating by the end. The stacatto brass and glissando strings characteristic of Xenakis' orchestral work are very much in evidence - this might be a long and complex work but it is thoroughly engaging. There's a few different recordings available - I went for this one as a 'best buy' based on reviews. Might pick up the 80s Australian recording at some point - that one apparently flits even more seamlessly between the live music and taped music, at the slight expense of some sonic clout.
Kraanerg - Col Legno release 2003