Pitch (or frequency) and volume (also known as amplitude) are two of the most fundamental qualities of sound, and both play a central role in how synthesizers shape audio.
Pitch and Frequency
Pitch refers to how fast the voltage inside a synthesizer oscillates between positive and negative values. These rapid fluctuations create a waveform, which can be visualized on an oscilloscope. The faster this oscillation, the higher the frequency.
In physical terms, this frequency controls how quickly the speaker cone moves back and forth. This motion vibrates the air, which then stimulates the eardrum and produces the sensation of pitch.
When the frequency of an oscillator is increased, the pitch of the resulting sound becomes higher. This corresponds to a tighter spacing between waveform cycles. Conversely, lowering the frequency results in a lower pitch and a wider spacing between the waveform cycles.
Pitch can be controlled manually using front panel knobs or automatically by applying voltage. Many synthesizers display the control voltage (CV) visually—for example, as a line that rises or falls depending on the voltage. A lower voltage typically produces a lower pitch, while a higher voltage results in a higher pitch.
Volume and Amplitude
Volume describes the strength or intensity of the oscillations that produce sound. This quality is determined by the amplitude of the waveform.
Lowering the amplitude results in a quieter sound, while increasing it makes the sound louder. On an oscilloscope, this can be seen as smaller or larger waveform heights.
Just like pitch, volume can be adjusted manually or controlled by voltage. One common method of doing this in a synthesizer is using a voltage-controlled amplifier (VCA) in combination with an envelope generator. The envelope shapes how the amplitude of a sound changes over time—defining aspects like attack, decay, sustain, and release.
By combining varying pitches with dynamic volume changes, synthesizers can produce expressive and musically interesting sounds.
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