Control Voltage, universally known as CV, is a variable voltage signal used to control parameters in analog synthesizers.

It is the analog precursor to MIDI. In an analog or modular synthesizer, instead of digital data, different electrical voltages are used to "tell" the components what to do.

The most common use of CV is to control the tuning of oscillators.

The most widespread standard is "1 Volt per Octave" (1V/Oct): If 1V corresponds to a C note, 2V will correspond to the next C an octave higher, 3V to the next, and so on. CV is also used to control virtually any other parameter, such as the cutoff frequency of a filter, the volume of an amplifier, or the speed of an LFO. To control an old analog synthesizer with modern equipment, a device called a MIDI to CV converter is needed, which translates the digital MIDI messages into the electrical voltages that the synthesizer understands.