An impulse response is a recording of how a space responds to a source of sonic excitation. Using processing, we can virtually place sounds inside that space, including derelict buildings that are inaccessible and spaces that no longer exist. The result is akin to a photograph: dense with information about a particular space, taken from a particular position. Additionally, it separates from what it represents: the acoustic comes away from the site and can be used on anything by anyone.

A reverberant building shapes what gets played in it, and if captured it can become something to compose with rather than an effect applied afterwards. The same technique works on things that were never rooms. Any sound can serve as a space to extrude others through, taking on its shape in the process, at which point the difference between a sound and a space stops being clear.

It follows that these recordings are also a form of documentation. Acoustic heritage is an established field, though attention tends to follow the buildings already considered significant, and most spaces deteriorate or come down without anyone having recorded them. Sound recording was first proposed as a way of preserving voices rather than selling music, so the preservation instinct was there at the start. A recorded voice is already affecting; placing one in a space adds situation, the space illuminated around it.

The talk moves through captured buildings, voices returned to rooms, and spaces played as instruments.