I just found an interesting link on the 360 Systems 20/20 Frequency Shifter: 360 Systems 20/20 Frequency Shifter (BODE) It gives a nice overview of how frequency shifters were used in some classic electronic music. Interestingly enough, the color scheme of the 360 Systems unit is very close to the ValhallaFreqEcho colors: This is pure coincidence, as I just found this post on Matrixsynth. The 360