Last month I mentioned a fundamental problem with two-channel playback:
the unlikely possibility of spatially realistic playback of any recording using loudspeakers. That's not to say that spatial effects don't occur with twochannel programmes - of course they do - but they are usually of the most phemeral variety.
There is a recording and playback technology capable of capturing realistic spatial cues and playing them back so effectively that even done-it-all audio experts are often astounded. It's called binaural recording, sometimes done with dummy head with small microphones placed where the ears would be.
Binaural recordings can also be done with specially fitted eyeglasses, with mics built into the stems or frames.

SOMETHING SPATIAL
Playing back such recordings over headphones is an amazingly realistic experience, a reach-out-and-touch-it kind of realism that isn't possible using loudspeakers. In fact, headphones are the only way that binaural realism can be heard, because the effect vanishes when
the recordings
are played back
over speakers. By
comparison with
what's possible
unaurally, the
spatial cues that
we hear in
surroundsound
mixes for
movies are crude
indeed, depending on and reinforced by screen visual information. Surround effects are usually most pronounced in wall-rattling action film soundtracks where sonic subtlety isn't a high priority.
But a good binaural recording heard through a good set of headphones can be spookily realistic, because all timing and location cues are preserved in their

proper relationships. A recording made in a small club captures not only the performers onstage, but the conversations and noise taking place all around you - without the need for anything more than two channels. The effect is private, of course, unless you and a friend have headphones connected to the same source, but a live recording can make you want to turn around and ask the nonexistent people behind you to please talk more quietly. imposes her own fiction on otherwise realistic tours of popular places, in often baffling ways. Her 1997 Chiaroscuro' tour of the San Francisco Museum Of Modern Art has participants don a set of headphones and look with one eye into the viewfinder of a video camera as they begin to climb the building's stairs. Everything looks

and sounds familiar, Cardiff's footsteps echoing your own. Then suddenly a panting phantom runs up from behind and dashes by. The effect is so real that you feel him brushing your arm as he passes. Cardiff's conflation of fantasy and reality is both disorienting and delightful.

STREET THEATRE
Among her many audio walks is The Missing Voice: Case Study B'. Commissioned in 1999 by Artangel, the 50-minute experience takes the adventurous on a stroll from London's Whitechapel Library to Liverpool Street Station. In the recording, Cardiff takes on the voices of her own fictional characters, interpreting and adding to the richness of all she sees and hears while walking through the city. She describes her narration as the sort of interior dialogue that is 'common to a lot of people, especially women, as they adjust to a strange city.' Snippets of Cardiff's audio tours can be heard on her website at www. cardiffmiller.com, but do take her advice: 'The tracks must be listened with headphones for the full 3D effect.'