At MoMA today, a player piano. I mean, a piano roll. I mean, whatever. A Bechstein grand with a hole cut out for a player to slip through - a player who has to play upside down, without the middle notes! On the other hand, the player can take the piano for a stroll while playing...
Jennifer Allora and Guillermo Calzadilla's "Stop, Repair, Prepare: Variations on Ode to Joy for a Prepared Piano" was even nicer from above, spinning people around it - even before the piano sallied forth, a tinny "Ode to Joy" echoing through MoMA's vast atrium.