Stereo width and the slow orbit

A steady tone with a steady noise bed has one significant weakness: you stop hearing it. Adaptation is fast and thorough, and within a few minutes a genuinely constant sound can drop out of awareness almost entirely.

That is sometimes exactly what you want. When it is not, the cheapest remedy is motion.

What the orbit is

Several sessions apply a very slow stereo movement — the sound field drifting between left and right over a period of tens of seconds. We describe it as an orbit, and its rate is published per session like every other parameter.

The rates involved are deliberately far below anything you would call a rhythm. Typical values sit around 0.01 Hz, which is one full traverse roughly every hundred seconds. That is slow enough that you never catch it moving. What you notice is that the field has not gone still.

The bound is 0.004 to 0.08 Hz. Below that, nothing perceptible happens. Above it, the movement becomes an event you track, which defeats the purpose and becomes irritating quickly.

Why not just add variation to the tone

Because variation in the tone is variation in the thing that is meant to be steady.

Changing the carrier introduces pitch movement, which is far more attention-grabbing than position movement — pitch is semantically loaded in a way that location is not. Changing the modulation rate changes the band, which is the parameter the session is built around. Changing depth changes how insistent it feels.

Spatial position is nearly the only property you can move without altering what the session is. It keeps the field alive while leaving the rhythm, the band and the level exactly where they were.

The interaction with binaural delivery

Worth understanding if you use binaural sessions.

A binaural beat is constructed from a frequency difference between the ears. A spatial orbit modulates the level difference between the ears. Those are separate cues and they coexist, but a deep orbit on a binaural session weakens the beat percept at the extremes of its travel, because one ear is receiving materially less of its tone.

Sessions that use binaural delivery therefore use shallower orbits than sessions that do not. On isochronic and monaural sessions, where the rhythm is in the signal rather than in the interaural difference, the orbit can travel further without costing anything.

The comparison of the three methods covers why the delivery mode changes what else the session can do.

Why it runs on the audio clock

This is an implementation detail with an audible consequence.

The obvious way to animate a slow pan is with a timer or an animation frame callback. Both are throttled or suspended when the tab is backgrounded or the screen locks — which is precisely when a long session is most likely to be running.

An orbit scheduled that way stops moving the moment you put your phone down, and resumes when you pick it up. The field goes still for twenty minutes and then lurches.

So the orbit is scheduled on the AudioContext timeline, along with the end-of-session fade and the sleep timer. The audio thread keeps running with the screen off, which means the motion is continuous whether or not anyone is looking at it.

Which sessions use it, and when it helps

Long sessions benefit most, because adaptation has time to set in. Tibetan Bowl Resonant Void at 33 minutes and Deep-Body Unwinding at 34 both use it.

Short, insistent sessions have less need — Flow State Gamma-Alpha Bridge has enough happening in its own trajectory.

For speakers, the orbit is subtler but still present. For sleep on a speaker across the room, it is close to inaudible and does no harm.