Tyler Green at Modern Art Notes has a chat with Stephanie Hanor, a curator from the Museum of Contemporary Art San Diego, about artists on the museum's wishlist. Among others, she mentions Sean Duffy, who did this "turntable piece" (above left). That's all well and good, but I hope Hanor, Green, and Duffy are familiar with Janek Schaefer, a sound artist/DJ who has been using a Tri-Phonic Turntable (above right) since 1997. Two of the tone arms on Schaefer's turntable face one direction and the third plays in reverse; he can also reverse the direction of the turntable itself and therefore invert the 2:1. What's more, he can stack records on top of each other, playing three records simultaneously on one turntable. More about Schaefer's turntable here. I'm not familiar with Duffy's work, and a cursory google seems to point to many other projects (turntable-related and not), but this one, at least, has been done (and better). Duffy's looks better, but on a purely functional level Schaefer's is far more interesting.