Learned that Seth Horvitz's Eight Studies for Player Piano was 'performed' at Mutek. interesting the idea of attending a concert without human performer. Basic Sounds attended and said this:
Seth Horvitz opened A/Visions 2 with his “Eight Studies for Automatic Piano.” Performed live without the presence of a human on stage, a single computer controlled piano played minimal repetitive rhythmic compositions. Visually you could see the keys going down on the piano, as if a ghost was playing. Projected behind the piano was a large linear line mimicking the keys, which helped the audience members have a better understanding of what was happening on stage.
'Helped the audience members have a better understanding of what was happening on stage' - in other words, plain old music is difficult to receive without assistance. Mediation is required.
Did Nancarrow have purely musical performances? None that I can find. Here's 'Study #21'
Instead we get reductions, realisations or transcriptions, as though the music can't be left to stand unplayed by human, that it only gains life / credibility once performed by living being. Here's the above '#21' arranged for trumpet, bassoon and guitar.
Even techno isn't allowed to take place without human agent - be it Ableton button pusher or DJ. I heard a rumour that Kraftwerk would play chess when performing live (nowadays, not with their old contraptions)
I attended a performance of Rytis Mazulis' player piano music at Huddersfield Festival in 2007 and they just played it through a stereo. Accompanying it however was a fluxus performance of somethign by fellow Lithuanian Georges Mancuinias which aside from their nationality had nothing to do with Mazulis' music.
Can't recall what the Maciunas piece was, but it wasn't this, which would have been much more approriate.
Performer-less performances of classical electronic music still takes place. Stockhausen's final published work Cosmic Pulses was staged at the Proms no less. The Melbourne Recital Centre has staged Xenakis works in their smaller room. I wonder whether they're performed in darkness or accompanied by some kind of pyrotechnics? Stockhausen was probably keen on the latter.