Synthesis

http://interface.khm.de/index.php/lab/experiments/arduino-realtime-audio-processing/

Tutorials
http://www.samplecraze.com/tutorial.php
http://www.soundonsound.com/sos/allsynthsecrets.htm
http://noisesculpture.com/how-to-make-a-noise
http://obiaudio.com/2010/07/09/how-to-program-a-synth/
http://academic.evergreen.edu/curricular/musictech/2006/arp2600.pdf