I just stumbled randomly upon this site:

http://www.capsgetpeeled.com/blog/archives/000413.html

"These pages document my final (graduate thesis) project at the Media Laboratory. The five month-long project concentrated on the development of a hardware/software interface for controlling musical events on a computer using a set of disk-jockey turntables and paper �records� that can be printed or drawn. These records contain visual markings representing programming information for synthesis and/or sequencing of music, which is optically interpreted by a plug-in cartridge (aka spinal cat) for the turntable tonearm. The cartridge then communicates with software on a host computer via MIDI or serial protocols."
The thesis is 30mb and i'm in the process of downloading it at the moment, but this is a very interesting concept to me. I am curious as to how the record tracks though, but ill definitely be giving this a go in the coming months and will post my progress here.