Vibrato

A delay line whose length changes while audio is running through it is a resampler. While the line is lengthening the output plays back slower and the pitch falls; while it shortens the output plays faster and the pitch rises. That is the whole mechanism, and it is why this is genuine pitch modulation rather than an amplitude effect wearing the name.

The line spans 5 ms and rests at its midpoint, with the LFO swinging symmetrically about that centre. Resting at the middle rather than at zero is what lets full depth use the entire range without the delay time ever going negative, and 5 ms is short enough that the delay itself is never heard as an echo.

Depth scales the LFO's excursion in seconds, so the pitch deviation it produces is the product of depth and rate, the rate of change of the delay length is what sets the interval, not the length. Doubling the rate at a fixed depth widens the wobble as much as doubling the depth does, which is worth knowing before reaching for the depth knob twice.

This is the browser preview: a DelayNode and an oscillator, structured after the reference vibrato rather than compiled from the same kernel, and making no parity claim against it. Nothing dry is summed inside the effect, unlike a phaser it is audible on its own, so the module's Mix is the only blend in the path. The line is mono, so there is no stereo spread here to speak of.