- Sound Engine
CVC versus Midi - A Case Study
The Moog Voyager is a wonderful sounding analog synth. It has two methods to control this sound engine externally, analog control voltages and Midi. In fact both can be used at the same time if one wishes.
Below are two sound files, one controlling the Voyager via control voltage from the CVC and the other via Midi. For these audio examples the same basic patch on the Voyager was used. The sound patch has a fast percussive blip at the beginning of it's filter and volume amplitude to accentuate the attack phase of a note shape.
Control Voltage (CVC) version
CVC control setup:
Gate = Filter and Volume envelope gates
X = pitch via the CV pitch input
Y = nothing
Z = Volume via the CV volume input
Midi Control setup (direct cabling from the Continuum Midi output to the Voyager Midi input):
Gate = generated as a Midi Note-On when Z becomes non-zero, Midi velocity at 127
X = Pitch
Y = nothing
Z = Volume control by sending Midi cc07 messages
No matter how fast the Continuum is played the percussive attack is slower via Midi than via the CVC. This is due to Midi data smoothing in the Voyager, and not a problem with the Midi protocol itself. The Voyager's smoothing is preventing it's VCA from responding to fast changes in Midi cc07, thus the percussive gate attacks are lost. In a typical Midi situation, cc07 wouldn't be used to generate fast transitional changes in the amplitude of a single note, as the Continuum is attempting to do via Midi. This is an example of how Midi implementation in a synth has been optimized for one purpose, preventing from being used in the more esoteric way that something like the Continuum requires. Fortunately a sophisticated synth like the Voyager has both Midi and control voltage paths for controlling it's sound parameters.