Rare Waves

Grendel Formant Filter


New - $229.00

Product tags


Four analog bandpass filters in parallel, plus a control voltage processor to articulate vowel like tones from your audio input.

Voltage to Language

The Grendel Formant Filter has three control voltage (CV) inputs: Size, Articulator X, and Articulator Y. These are optimized for 5 volt analog control signals, but can accept up to +/-10 volts.

The Size parameter moves all four BPFs in parallel. This affects the overall size of the filter’s ‘mouth’, from oversized to midget.

Articulators X and Y work together to select vowel tones from a two-dimensional map related to the IPA Vowel Chart. For optimum control, these inputs can be connected to an analog joystick controller or two channels of a MIDI-CV converter. The ideal voltage range for controlling Articulators X and Y is +/- 2.5 volts, or 0..+5 volts. See the Patching Guide for further detail.

vowel chart with pronunciation

Suggested signal sources for the CV inputs are LFO, envelope generator, MIDI-CV converter, analog joystick controller, etc…

Q. How has it changed from version 1 (released in 2012)?

A: The control processor has been optimized for full control with fewer parameters. The functions of Articulators I,II, and III have been condensed into Articulators X and Y. The BPF on/off switches have become obsolete in the new order and have been assimilated. In addition, input and output signal levels have been standardized. In all other regards, the filter bank is identical.