Spatial audio is one option in immersive, not the point of it.
Spatial audio gets discussed as though it were the whole of immersive sound. It’s one option among several, and worth being clear about when it earns its place.
It works because it matches how hearing works outside a theatre. You sit inside a bed of ambient sound arriving from every direction and every height, and out of that bed particular sounds get picked out and pull your attention. That selection isn’t aesthetic — it’s almost certainly survival machinery. The first question the ear asks of a sound is whether it represents a threat. I’ve written about the related effect in forests.
In a dome or a headset that becomes useful, because the viewer doesn’t necessarily know where to look. If a whale enters an underwater scene at the top left of the dome, sound can say so before the eye finds it. And there’s no rule that only effects can do that job — a musical element can be placed too.
I’d rather be honest about the limits: there isn’t much here that can be stated definitively. What I have is what I’ve done. Localising a solo instrument to an imagined space in the dome. In Mars 1001, answering the pre-launch fanfare antiphonally — trumpets in front, then behind to the left and right.
None of which is new. Antiphonal writing is old concert-hall practice: forces separated and deliberately placed. Britten specifies it in the War Requiem, where the boys’ choir is meant to sound distant and apart from everything else.
I sang that. Christ Church again, this time under Simon Rattle with the City of Birmingham Symphony Orchestra at Birmingham Town Hall, and “off stage” was taken literally — a room high up towards the back right of the hall, singing through a door left ajar so the sound would carry into the auditorium.
That’s spatial audio with no technology in it whatsoever. The dome only gives you more control over where the door is.