A stereo waveshaper whose one big knob is a harmonic number. Instead of asking "how much distortion?", Chebyshev asks "which harmonic?", and turns what you feed it into that harmonic.
The idea
Chebyshev polynomials have a tidy property: put a pure sine through the polynomial of order n and what comes out is the nth harmonic of that sine. Order 2 gives the octave above, order 3 the octave and a fifth, order 4 two octaves up. So moving the Order knob does not make the effect stronger, it makes it sound like a different interval.
That holds cleanly only for a sine. Real material has many partials, and each one is transformed at once, so on chords and rich sounds the higher orders turn into dense, bright, metallic grit rather than a neat transposition. Single sustained notes are where the harmonic character is easiest to hear.
Controls
- Order (1 to 100) picks the polynomial, and with it the harmonic. Order 1 passes the signal unchanged. Low even orders (2, 4) add octaves and thicken; low odd orders (3, 5) add fifths and a hollow, reedy colour; high orders become bright inharmonic sheen.
- Mix blends the shaped signal with the dry one. High orders remove most of the original fundamental, so keeping some dry signal is usually what makes the result sound coloured rather than replaced.
The panel draws the shaping curve and the blended result for the current settings, so you can see how many times a high order folds the waveform.
Getting started
Chebyshev is an audio effect for any stereo source. A clean, sustained guitar or synth note shows the effect most clearly. Try the presets:
- Octave Thicken: order 2 blended in, a musical way to fatten a bass.
- Fifth Ghost: order 3, a fifth nobody played, kept low as colour.
- Hollow Square: order 5 well up in the mix, reedy like a clarinet.
- Two Octaves: order 4 fully wet; the fundamental all but disappears.
- Metal Sheen: order 80 kept quiet, bright grit on top of the source.
- Default: order 50 at half mix.
High orders are steep curves that would normally alias badly; Chebyshev processes them at four times the sample rate with filtering to keep the upper half of the range usable.
