Frequency Shifter

A single-sideband frequency shifter in the Bode / Moog 914 tradition. It adds a constant offset in Hertz to every frequency in your signal — turning harmonic, tonal material metallic and inharmonic, with a stabilized feedback path that sings into endless-glissando self-oscillation. Stereo in, stereo out, no latency.

How it works

Unlike a pitch shifter, which preserves harmonic ratios, this shifts every partial by the same number of Hertz — so an evenly-spaced harmonic series becomes a clangorous, bell-like spread that no longer maps to a pitch. Internally a Hilbert allpass pair splits the signal into two copies 90° apart, then an internal carrier oscillator demodulates them to move the spectrum up or down. The feedback path is DC-blocked and soft-saturated, so you can push it hard without it blowing up.

Controls

  • Shift — the offset applied to the whole spectrum, bipolar around a center detent (no shift, pass-through). Small amounts add shimmer and beating; large amounts go fully inharmonic. Its full reach is set by Range — ±500 Hz at the default.
  • Range — scales how far Shift can travel, from a hair-fine 20 Hz span up to a clangorous 5000 Hz. Keep it narrow to pack sub-Hz beating and chorus-like detune right around the center; open it wide to reach the extreme Bode-style metallic zone.
  • Fbk — feeds the shifted output back through the shifter, up to 0.85. Up from zero it thickens and rings; near the top it self-oscillates into a slow, sliding glissando.
  • Drive — sets how hard the feedback path is pushed into its soft-saturator, from 0.05 to 0.6. Low keeps the self-oscillation clean and ringing; high makes it grittier and compresses sooner. Only audible once Fbk is up.
  • Mix — dry/wet blend. Fully wet by default; back it off to keep the original underneath the shifted layer.

Inputs & outputs

  • In L / In R — the stereo signal to process; the two channels are shifted independently, so input stereo width is preserved.
  • Shift / Range / Fbk / Drive / Mix CV — voltage control over each knob, summed with its setting. Patch an LFO or envelope here for moving, breathing timbres.
  • Out L / Out R — the shifted stereo result.

Tips

  • Tiny shifts (a few Hz, knob just off center) give lush chorus-like beating without losing the source's pitch.
  • Crank Fbk with no input to let the shifter ring on its own, then sweep Shift for ghostly rising or falling tones.
  • Modulate Shift CV with a slow LFO for a barber-pole, never-ending-glide effect.
  • Open Range wide and push Shift hard for clangorous, bell-like metallics; keep it narrow for delicate sub-Hz beating.