The VM901ABBB is an oscillator bank that replicates the unique oscillator controller/slave arrangement of classic Moog synthesizers. The concept is that the the Oscillator Controller module sets the overall coarse tuning as well as rectangular wave pulse width for the three slave oscillators. In the original hardware modular systems, the controller oscillator and slaves were connected internally. Any number of slave oscillators could be used, but the "one+three" combo was common, and we felt it represented a good compromise of utility and size. Though these have the appearance of four individual single-width modules, VM901ABBB is a single quad-width module. VM901ABBB accurately replicates the sound of the earliest Moog oscillator design.