Just to get going - a short explanation of the mechanical components I laid out in the project photo:

• A manual slider (either 3D printed or carved out of wood) will contain a micro-switch.
• The slider will be actuated by hand, and guided on a round 600x8mm linear rail such as used in 3D printers by the 8mm bushings seen middle-right.
• Micro-switch will close a circuit by the slider touching two strips of copper tape (top center).
• The bead chain (top-left) will transmit movement from a slider onto a 3D printed pulley.
• 3D printed pulley (yet to be printed) will be mounted on a D-shaft (center).
• D-shaft will be mounted through two lipped ball-bearings (second from top, both left and right) in Actobotics U-bracket (top-right).
• Flex-coupler will transmit rotation of D-shaft to 10xRotation potentiometer.
• Position of the pot will be read by the 16-bit ADC.

I really hope to get the UI shield from my other project here by next week, and getting going again with this project by placing the 8-bit synth output components on a prototyping shield.