The modular system once developed by Robert "Bob" Moog went through a long production period between 1964 and 1981, including its development process. At that time, the new, electronic instrument was an avant-garde pioneering work that still had to be explained to the public, but ultimately found more and more interested parties. Behringer has transferred the generously dimensioned dimensions to the compact Eurorack format and paid close attention to ensuring that the sound and function are in no way inferior to the cult object.

The 911 Envelope Generator from Behringer is a classic ADSR envelope with the percussive amplitude curve familiar from the famous System-55. The control times for the three time phases can be set between 10ms and 10s.