Jeremy Bell has been experimenting with tape scratching for some years [check his Youtube channel], and now he's refined some of those early experiments into what he calls the ScrubBoard. Its essentially a 2 inch tape loop device but where the user manually plays the position of the playback and and record head or "painting" as he calls it.
In the first video, Jeremy takes us through the process of building a loop, and in the second (see below) he's got some more examples how what he can do with it.
Its still got a ways to go before production, as there's a bit of disconnecting and reconnecting going on, but we think its delightfully inspiring. Keep doing what you do Jeremy...
This would make a great iPad app wouldn't it? Though a hardware version would be way more fun.
More info:
http://thescrubboard.com
Thanks to MagicalSynthAdventure (Paulee Bow) for the find.