Pitch Shifter

Shift Amount Display Shows the current pitch shifter interval.
Shift Amount Knob Sets the pitch shifter interval.
Fine Knob Fine-tunes the amount of pitch shifting.
Input Frequency Source Sets whether the pitch of the input signal is detected automatically or not.
Auto-detect Indicator When in auto-detect mode, this lights up when the input signal pitch is successfully detected.
Input Frequency Knob In manual mode, use this to calibrate the module to the pitch of the input signal.
Pitch Input If the pitch of the input signal is available in you patch as a 1V/octave CV signal, connect it here and leave the Input Frequency knob centered (manual mode only).
Inputs Audio signal that will be pitch-shifted (stereo).
Outputs Pitch-shifted audio signal (stereo).

Overview ⚓︎

The Pitch Shifter module changes the pitch of an audio signal.

The interval can be selected between -3 and +3 octaves by turning the Shift Amount knob, or perhaps more easily by clicking on the Shift Amount display and selecting an interval between -1 and +1 octave from the menu.

Usage ⚓︎

Connect an audio signal to the lower-left input, connect the output to the Output Mixer or another point in the audio signal path or your patch, and adjust the shift amount.

Whenever possible, try to use the module in auto-detect mode, where the pitch of the input signal is automatically detected. Otherwise, it will need to be calibrated manually.

In auto-detect mode with stereo inputs, the pitch is only detected from the left channel. It is not possible to use a single Pitch Shifter module to process two mono sources with different pitches.

Calibration ⚓︎

Pitch shifting works better when the pitch of the input signal is known. By default, the pitch is auto-detected with a built-in pitch detector. This works well for many sources, but isn’t always perfect. See the limitations of the Pitch Detector module for an idea of what sources will work in auto-detect mode.

In some patches, it may be better to calibrate the module manually. This can be done by switching to manual mode and either setting the input frequency manually with the Input Frequency knob, or leaving that knob centered and connecting a 1V/octave pitch signal to the Pitch input.

For polyphonic, unpitched or complex signals, the best choice is usually to set the Input Frequency knob to an arbitrary low value. It will add a wobbly texture, but this can be used creatively. However, be aware that lower Input Frequency values introduce more delay in the output signal.

Internal Algorithm ⚓︎

In order to fully take advantage of the Pitch Shifter, it can be useful to know how it works internally. Here is a simplified description of the algorithm:

The input signal is recorded into a short delay line.
A read head advances in the delay line faster or slower than the signal is being recorded, depending on the amount of pitch shifting.
As the read head approaches the end of the delay line, a second read head gradually takes over at an earlier or later point (depending on whether we shift up or down, respectively).
The distance between the read heads is calibrated with the Input Frequency settings. If it matches the source pitch, the transition between the read heads will be seamless.

Since the distance between the read heads varies with the input frequency, you may hear clicks when the input pitch changes. This is usually unnoticeable when the signal is being pitch-shifted, but becomes obvious when the shift amount is set to Original (no pitch shifting). In some patches, when this happens, it can be a good idea to set the Input Frequency to manual mode so that the distance between the read heads remain constant.

Granular Resynthesis ⚓︎

The pitch shifting algorithm can be considered a subset of granular synthesis since it operates on small, granular segments of audio signals.

In the spirit of sonic experimentation, we strongly encourage the off-label use of the Pitch Shifter module to explore real-time granular resynthesis:

In manual mode, the Input Frequency knob controls the grain size (the distance between the alternating read heads).
The Shift Amount knob controls the playback speed of the most recently generated grain.

By setting or modulating these two knobs in ways that are not correlated to each other or to the source pitch, it is possible to achieve interesting audio-mangling real-time granular effect.