BARKHAUSEN

This spectral/vocoder effect playground exposes a bunch of effects from the constant Q transform.

It has all the classics, formant control, pitch-shifting, comb filtering, delay / feedback, brick-wall high / low cut, and more.

Sadly, it only works on M series Mac's. This is because it needs the GPU's concurrent speed and I can only program for my hardware. Hopefully this changes soon.

What sets it apart though, is the constant Q transform and its "inverse". The constant Q transform calculates logarithmically spaced frequencies as opposed to the linear spacing of the Fourier transform meaning it will stay in tune. Each frequency is calculated concurrently and as soon as possible making it almost real time, it has a delay of ~30 cycles for every frequency which creates a very metallic sound.

As you may have noticed, inverse is in quotes. The constant Q transform inherently has no true inverse, meaning the output signal won't sound exactly like the input. That's where the creative freedom comes from though.

make you're instruments sound as weird as possible.

effects:

Constant Q transform options

The initial Q option is set to 24, meaning it calculates 24 quarter tones per octave, this allows it to distinguish between semitones as there's a quarter tone in-between each one. However, it also has 12 and 6 options, these are inherently less accurate but create a nice low-bitrate effect especially at 6.

The mapping of input -> output frequencies is also randomizable at four varying degrees. 6 means the frequency is place randomly up to 6 quarter tones (at 24 Q factor) from the original frequency and so on. This can make vocals sound like a different person with a small offset or like complete distortion at a higher offset.

Also note, changing these settings resets all the frequencies phase to 0 which, for lack of a better words, makes a cool BEEOOUWW sound. (this will optionally reset to randomized frequencies to remove the BEEOOUWW sound in a future update).

Delay / feedback

Because each frequency takes a little longer than the last, the delay time is determined by the frequency and a slider. The lower side having a longer delay to the higher side creates a vast, other-wordly sound.

The feedback is also very customisable. The delayed signal can come from four different points in the signal chain or the opposite channel.

Comb filtering

unlike classic comb filtering which is achieved using an FIR/IIR filter, this uses the fact that the calculated frequencies are already on the equal temperament scale. It gates specified notes with optional unison, automatic chords and MIDI input.

Brick wall EQ - thresholding

EQ'ing is also classically achieved with filters, however, in the frequency domain it's trivial to just cut everything below or above a frequency. This also creates a brick-wall style filter, meaning there is no roll off, just on or off.

The thresholding is maybe better called decimation. It stores a number of the loudest frequencies, the number being controlled by the slider, to only let the loudest frequencies through. This creates a very sparkly sound especially when feed back.

Pitch-shifting

the pitch shift slider simply moves the whole frequency content up or down, however, because the frequencies are tied to notes, the amount it shifts is specified by semitones rather than arbitrary FFT bins.

Formant control

unlike pitch-shifting, formant control isn't quantized to semitones. It's fast response and wide frequency range makes it sound almost like a vinyl stop, this is why I made it a horizontal slider that ranges from -1 to 1, giving it the same feel as a DJ deck cross-fader.