Sub:Pulse Wave Modulation and...
Pulse Wave Modulation and Serial Filtering
Pulse wave modulation (PWM) is a technique used to manipulate the pulse width of a waveform, typically of a square wave. PWM can be used to create subtle movement to an otherwise static sound by modulating the pulse width over time.
When a waveform is modulated using PWM, the width of the pulses in the waveform is varied, which changes the harmonic content of the sound.
The top waveform below shows a perfect Square with 50% on and off “duty cycles”.
This creates a range of different timbres and textures, from bright and sharp to mellow and rounded. PWM can be used to create a wide variety of sounds, including basses, leads, pads, and sound effects.
The Pulse Width can be modulated using an LFO. The LFO can then be synced to the tempo which can create interesting rhythmic patterns.
Serial filtering is a technique used to apply multiple filters in series to a sound or signal. When filters are applied in series, each filter processes the sound and removes or modifies certain frequencies, and the resulting sound is then passed through the next filter, which further processes the sound. In the Analog example below Filter1 is sent 100% to Filter 2 so we can selectively remove some low frequencies in addition to removing highs with Filter 1.
This technique can be used to provide additional frequency shaping that could not be achieved with one filter type only.. For example, a high-pass filter can be used to remove low frequencies from a sound, while a low-pass filter can be used to remove high frequencies. By applying these filters in series, the resulting sound can be shaped in a more complex and nuanced way.
Serial filtering can also be used in conjunction with Saturation (Drive). For example, a sound could be filtered to remove certain frequencies, then passed through a saturation distortion effect to add additional color and grit, and then modulated using an LFO to create movement and interest.