Controlling Pitch On a String Instrument

Eye candy

Clapper solenoids aka instrument a day: http://www.flickr.com/photos/ranjit/3317186605/

Tension Guitar: http://www.moonmilk.com/2008/02/23/thing-22-automatic-tension-guitar/

Guitar bot- sliding tuner: http://www.youtube.com/watch?v=HxLTJmmyqn4

LEGO NXT tuning system: http://www.youtube.com/watch?v=6BUmIY5aR_M&feature=related

Hydraulics: http://www.youtube.com/watch?v=Elt1XriaQXU&feature=related