DIY Midi Drum Links

http://drummagazine.com/dont-pull-that-trigger/
https://forum.pjrc.com/threads/31797-Teensy-FSR-based-MIDI-controller
http://www.pjrc.com/teensy/td_midi.html
http://www.paia.com/ProdArticles/drumsens.htm
http://www.instructables.com/id/Pringle-Can-MIDI-Drums/?ALLSTEPS
https://beammyselfintothefuture.wordpress.com/2015/01/28/sensing-hit-velocity-and-quick-subsequent-hits-of-a-piezo-with-an-arduino-teensy/
http://todbot.com/blog/2006/10/29/spooky-arduino-projects-4-and-musical-arduino/
http://www.learningaboutelectronics.com/Articles/Voltage-follower
http://electronicdesign.com/analog/op-amps-make-precision-clipper-protect-adc
http://www.robotoid.com/appnotes/sensors-piezo-disc-touch-bar.html
http://electronics.stackexchange.com/questions/248308/op-amp-diode-clamping-circuit
https://sourceforge.net/projects/yaamidrum/

Programming Audio Units

Audio Units on Mac OS X Mavericks (10.9) and Xcode 5

Making Audio Plugins

Watchmaking/Jewelery

Places to buy books:
http://timesavers.com/