Recording a scene

Everything so far synthesized scenes. But Chapter 2 flagged the scene-based paradigm's exclusive: it's the one you can point a microphone at. A single instrument on a stand captures the actual soundfield of a forest, a cathedral, a protest, a rehearsal — behind, above, all of it — as a bus your whole toolkit already speaks.

This chapter is the field guide's field chapter: how the microphones work, what the market looks like, and the craft that makes location B-format worth keeping. (Ecosystem facts here are stated as of 2026; models drift, principles don't.)

A-format and B-format

Chapter 6's ideal — an omni and three figure-8s occupying one point — cannot be built; microphones have bodies. The 1970s solution (Gerzon and Craven's, still the standard design) is the next best thing: four cardioid capsules on the faces of a tiny tetrahedron, as close to coincident as manufacturing allows.

The raw four-capsule output is called A-format — four aimed cardioids, useless directly. But within the coincidence approximation, sums and differences of the four reconstruct the ideal set exactly: all four capsules summed ≈ the omni W; front pair minus back pair ≈ the X figure-8; and likewise Y and Z. That matrixing (plus filters correcting the "tiny but not zero" spacing) is the A-to-B conversion, and it ships with every mic as a plugin or is done on-board. The output is B-format — and after Part II you know precisely what that means, down to asking the professional's three questions (order? channel order? normalization?). Modern mics emit AmbiX; vintage material and the classic SoundField lineage speak FuMa; format~ (Chapter 8) stands at the border.

Higher orders need more capsules — the (N+1)² economics again, now in hardware: order 2 wants ~8+ capsules, order 4 wants ~32 arranged on a rigid sphere, and the conversion mathematics gets correspondingly heavier. This is Chapter 7's "microphones lag encoders," explained.

The market, in tiers (2026)

  • Recorder-integrated, first order. The Zoom H3-VR class: four capsules, A-to-B conversion, level-metering and an SD card in one handheld box. The field-recording workhorse tier — point at the world, get AmbiX WAV.
  • Studio-grade first order. The Sennheiser AMBEO VR, Rode NT-SF1, and the SoundField heritage line (now under RØDE/Freedman): better capsules, XLR outputs, conversion in a plugin where you can choose the output convention. The tier for material that will be mixed hard.
  • Higher-order arrays. Spherical rigid arrays: Zylia's ZM-1 class (order ~3 from 19 capsules) and the research-and-broadcast Eigenmike em32/em64 (orders 4–6). Costs jump an order of magnitude; so does the post-processing. Rent before buying; verify your whole chain handles the channel counts.
  • Adjacent but not ambisonic: binaural head rigs record two-channel ear signals (lovely, but baked — Chapter 13's format, not a scene), and spaced multichannel trees capture enveloping channel-based material (fold it in with bed2hoa~ if you must, remembering what it is).

Field craft

The handful of practices that separate keeper B-format from expensive regret:

  • Orientation is sacred. The mic's marked front is your scene's 0° forever after. Photograph the setup; note "front = stage" in the slate. A mounted-sideways surprise costs an afternoon of rotate~ forensics (and an upside-down one is why flip_ud exists — Chapter 15's rescue list, written from experience).
  • The mic is the listener's head. Where you stand it is where every future listener stands. Height matters (ear height reads natural; 3 m up reads crane shot). Proximity matters doubly: nearby sources dominate a coincident array fast — the "step back" your recording teacher preached, now in 360°.
  • Wind and handling travel in W. Standard protections (blimps, suspensions) apply — fourfold. Any thump is omnipresent by definition.
  • Monitor binaurally on location: mic → binaural~ 1 is a two-object patch (or the recorder's own binaural fold-down), and it catches the orientation and proximity mistakes while they're still fixable.
  • Slate the paperwork: order, convention (the recorder's manual knows), sample rate, and orientation notes, in a text file beside the WAVs. Chapter 8 predicted this file; be the collaborator who ships it.

Recorded scenes in the toolkit

Back home, a recorded scene is just a bus with weather in it — every Part III tool applies. The idioms that come up constantly:

  • Re-aim in post: rotate~ turns the whole location; the take where the action drifted 40° left is salvageable.
  • Interview the field: vmic~ beams extract usable mono spot "mics" from a scene recorded with none (order-limited, but astonishing the first time).
  • Recorded bed + synthetic foreground — the hybrid Chapter 7 recommended: first-order forest as the world, order-3 encoded sources as the story. Sum the buses (pad the first-order scene's 4 channels into the order-3 cord) and the seam is inaudible.
  • Stabilize handheld moves the same way VR does: record the mic's orientation (IMU or careful notes), counter-rotate in post — Chapter 4's head-tracking machinery, pointed backwards in time.

Checkpoint

Tetrahedra of cardioids → A-format → matrixed to B-format; first order is a handheld commodity, order 4+ is a spherical-array specialty; orientation, placement, and paperwork are the craft; and a recording is just a bus you didn't have to patch. One question remains before the DAW chapter poses it everywhere: your scenes — synthetic or recorded — eventually have to ship. Onward to the toolchains the rest of the industry mixes in.