CV/gate (an abbreviation of control voltage/gate) is an analog method
of controlling synthesizers, drum machines and other similar equipment
with external sequencers. The control voltage typically controls pitch
and the gate signal controls note on-off.
This method was widely used in the epoch of analog modular
synthesizers and CV/Gate music sequencers, since the introduction of
Roland MC-8 Microcomposer
Roland MC-8 Microcomposer in 1977 through to the 1980s, when it
was eventually superseded by the
MIDI protocol (introduced in 1983),
which is more feature-rich, easier to configure reliably, and more
readily supports polyphony. The advent of digital synthesizers also
made it possible to store and retrieve voice "patches" - eliminating
patch cables and (for the most part) control voltages. However,
numerous companies – including Doepfer, who designed a modular
Kraftwerk in 1992 Buchla, MOTM, Analogue Systems, and
others continue to manufacture modular synthesizers that are
increasingly popular and rely primarily on analog
CV/gate signals for
communication. Additionally, some recent non-modular synthesizers
(such as the Alesis Andromeda) and many effects devices (including the
Moogerfooger pedals by Moog as well as many guitar oriented devices)
CV/gate connectivity. Many modern studios use a hybrid of MIDI
CV/gate to allow synchronization of older and newer equipment.
1 Basic usage
2 Modern usage
3 See also
5 External links
In early modular synthesizers, each synthesizer component (e.g., low
frequency oscillation (LFO), voltage controlled filter (VCF), etc.)
can be connected to another component by means of a patch cable that
transmits voltage. Changes in that voltage cause changes to one or
more parameters of the component. This frequently involved a keyboard
transmitting two types of data (CV and gate), or control modules such
as LFOs and envelope generators transmitting CV data:
Control voltage (CV) indicates which note (event) to play: a different
voltage for each key pressed; those voltages are typically connected
to one or more oscillators, thus producing the different pitches
required. Such a method implies that the synthesizer is monophonic. CV
can also control parameters such as rate, depth and duration of a
Gate (sometimes called "trigger") indicates when a note should start,
a pulse that is used to trigger an event, typically an ADSR envelope.
In the case of triggering a drum machine, a clock signal or LFO square
wave could be employed to signal the next beat.
While the concept of CV was fairly standard on analog synthesizers,
the implementation was not. For pitch control via CV, there are two
Volts per octave: this standard was popularized by
Bob Moog in the
1960s; it was widely adopted for control interfacing. One volt
represents one octave, so the pitch produced by a voltage of 3v is one
octave lower than that produced by a voltage of 4v. Notable followers
of this standard include Roland, Moog, Sequential Circuits, Oberheim
and ARP. This standard also required control modules to carry the
source voltage (B+, 5v) on the ring of a TRS jack, with the processed
voltage returning on the tip. However, many other manufacturers have
used different implementations with voltages including -5 to 5v, 0 to
5v, 0 to 10v with the B+ possibly on the tip. This makes
interoperability of modules problematic.
Hertz per volt: this method (used by most but not all
Korg and Yamaha
synthesizers) represents an octave of pitch by doubling voltage, so
the pitch represented by 2v is one octave lower than that represented
by 4v, and one higher than that represented by 1v.
The following table demonstrates some notes and their corresponding
voltage levels in both implementations (this example uses 1v per
octave and 55 Hz/v):
Volts per octave scheme, V
Hertz per volt, V
Generally, these two implementations are not critically incompatible;
voltage levels used are comparable and there are no other safety
mechanisms. So, for example, using a Hz/volt keyboard to control a
volts/octave synthesizer will eventually produce some sound, but it
will be completely out of tune. Commercial solutions are available to
get around this problem, most notably the
Korg MS-02 CV/trigger
On synthesizers, this signal is usually labelled as "CV", "VCO in",
"keyboard in", "OSC" or "keyboard voltage".
CV, as applied to control of other parameters usually follows a
pattern of minimum to maximum voltage. For example, the Moog modular
synthesizers also use the 0-5v control voltage for all other
parameters. They are represented on the front panel of many
synthesizers as knobs, but often a patch bay allows the input or
output of the related CV to synchronize multiple modules together. So,
for example, the pitch voltage from a keyboard could also be used to
control the rate of an LFO, which could be applied to the volume of
the oscillator output, creating a tremolo that becomes faster as the
pitch rises. Modules that can be controlled by CV include VCF, VCA,
high and low frequency oscillators, ring modulators, sample and hold
circuits and noise injection.
Gate (trigger) also has two implementations:
V-trigger ("voltage trigger", sometimes called "positive trigger"):
this method involves keeping normally low voltage (around 0 v) on
trigger and producing a fixed positive voltage to indicate a note is
on. The amount of voltage required differs from synthesizer to
synthesizer, but generally it is from 2 to 10 v. V-trigger is used by
Sequential Circuits synthesizers, among others.
S-trigger ("short circuit trigger", sometimes called "negative
trigger"): this involves keeping voltage high normally, shorting the
trigger circuit whenever the note should play. S-trigger is used by
Korg and Yamaha synthesizers, among others.
Depending on the voltage level used, using the wrong combination of
triggering mechanism will either yield no sound at all or reverse all
keypress events (i.e. sound will be produced with no keys pressed and
muted on keypress).
On synthesizers, this signal is usually labelled as "gate", "trig" or
Since the publishing of the
MIDI standard in 1983, usage of
control synthesizers has decreased dramatically. The most criticized
aspect of the
CV/gate interface is the allowance of only a single note
to sound at a single moment of time.
Shortly after the
MIDI standard came out Roland introduced the Roland
CV/gate converter that takes an input from four
MIDI channels; i.e. a variable base
MIDI channel plus the next three
MIDI channels and converted up to four
MIDI channels into
CV/gate outputs able to control four separate CV/gate
synthesizers or a four-voice synthesizer like the
Oberheim 4 voice
analog synthesizer which is made up of four separate monophonic SEM
However, the 1990s saw renewed interest in analog synthesizers and
various other equipment. In order to facilitate synchronization
between these older instruments and newer MIDI-enabled equipment, some
companies produced several models of CV/gate-
MIDI interfaces. Some
models target controlling a single type of synthesizer and have fixed
CV and gate implementation, while some models are more customizable
and include methods to switch used implementation.
CV/gate is also very easy to implement and it remains an easier
alternative for homemade and modern modular synthesizers. Also,
various equipment, such as stage lighting, sometimes uses a CV/gate
interface. For example, a strobe light can be controlled using CV to
set light intensity or color and gate to turn an effect on and off.
With the advent of non-modular analog synthesizers, the exposure of
synthesizer parameters via
CV/gate provided a way to achieve some of
the flexibility of modular synthesizers. Some synthesizers could also
CV/gate signals and be used to control other synthesizers.
One of the main advantages of
MIDI is in the resolution.
MIDI control message uses seven bits or 128 possible
steps for resolution. Thirty two controls per channel allow MSB and
LSB together to specify 14 bits or 16,384 possible steps of total
resolution. Control voltage is analog and by extension infinitely
variable. There is less likelihood of hearing the zipper effect or
noticeable steps in resolution over large parameter sweeps. Human
hearing is especially sensitive to pitch changes, and for this reason
MIDI pitch bend uses 14 bits fundamentally. Beyond the 512 directly
defined 14-bit controls,
MIDI also defines tens of thousands of 14-bit
RPNs and NRPNs, but there is no method described for going beyond 14
A major difference between
MIDI is that in many analog
synthesizers no distinction is made between voltages that represent
control and voltages that represent audio. This means that audio
signals can be used to modify control voltages and vice versa. In MIDI
they are completely separate however, and additional software such as
Expert Sleepers is required to convert analog CV signals into
MIDI control data.
Some software synthesizers emulate control voltages to allow their
virtual modules to be controlled as early analog synthesizers were.
Propellerheads Reason allows myriad connection
possibilities with CV, and allows gate signals to have a "level"
rather than a simple on-off (for example, to trigger not just a note,
but the velocity of that note).
Mark of the Unicorn released a virtual instrument plug-in,
Volta, allowing Mac-based audio workstations with
Audio Units support
to control some hardware devices. CV control is based on the audio
interface line level outputs, and as such only supports a limited
number of synthesizers.
In recent years, many guitar effects processors have been designed
with CV input. Implementations vary widely and are not compatible with
one another so it is critical to understand how a manufacturer is
producing the CV before attempting to use multiple processors in a
system. Moog has facilitated this by producing two interfaces designed
to receive and transmit CV in a system, the MP-201 (which includes
MIDI) and the CP-251. Examples of effects allowing the use of CV
include delays (Electroharmonix DMB and DMTT, Toneczar Echoczar,
Line6, Strymon and others), tremolo (Goatkeeper), Flange (Foxrox
Paradox), envelope generators/lowpass filters/ring modulators (Big
Briar, WMD) and distortion (WMD).
Open Sound Control
^ Russ, Martin (2012). Sound Synthesis and Sampling. CRC Press.
p. 192. ISBN 1136122141. Retrieved 26 April 2017.
^ Dominic Milano, Mind over MIDI, Hal Leonard Corporation, 1988, p.1.
^ The Minimoog, released in 1971, had no patch cables; making a more
portable instrument by restricting options - but with no storage.
^ Brent Hurtig,
Synthesizer basics. Hal Leonard Corporation, 1988,
Gates and Triggers tutorial at Synthesizers.com
Analogue Solutions' Beginner's guide to MIDI-CV conversion — a
detailed article on all aspects of M