CRQL has launched Crumpets, an audio plugin designed to separate and shift formant and harmonic content within an audio signal. The plugin uses cepstral processing to provide independent control over these elements, including separate adjustment of mid and side formant information.
The name Crumpets is an anagram of “cepstrum”, referring to the signal-processing domain used by the plugin. A cepstrum can be described as the spectrum of a spectrum, and can be used to distinguish characteristics associated with a sound’s spectral envelope, or formants, from its harmonic structure.
According to CRQL, Crumpets processes incoming audio into formant and harmonic cepstra. These are transformed back into frequency-domain components, allowing the formant shape to be adjusted before the signals are shifted, re-convolved, and returned to the time domain. The process is intended to work with polyphonic formant material.
Crumpets provides a cepstrum display in which formants are shown in orange and harmonics in blue. Its main controls include:
- Res, which sets the cepstral cutoff used to separate formant and harmonic information.
- Mid and Side, for shifting formant information in the corresponding mid and side channels.
- Mix, providing a dry/wet balance from 0 to 100 percent.
- Gate, which controls cepstral gating on the input signal.
The plugin also includes Auto mode for monophonic cepstrum cutoff tracking, along with MIDI control of the cepstrum cutoff. A Lock function links the Mid and Side shift controls so that both channels can be adjusted together.
Crumpets is available from the CRQL website for £13.00.
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