Once upon a time, surround sound was very much touted as The Next Big Thing. What's more, in the movie and video game worlds, its promise has been fulfilled. However, in the music sector, the benefits and possibilities of multi-channel audio aren't getting people as excited as they once did.

This raises various questions: is it simply the case that listeners have no appetite for surround sound music. or are there technical and cultural reasons why producers don't mix for more than two speakers? And if surround setups have no future for music, what kind of potential is there to get a '3D' experience from our existing hardware. or to experience it in a live context? Perhaps the biggest reason surround sound has failed to capture the public's imagination is that audiences have been busy with other technology - MP3, iPods, etc.

Dr Bill Gardner is president of plug-in developer Wave Arts and has written extensively on the subject of 3D audio processing. He recognizes that the current climate isn't really conducive to the widespread adoption of true surround listening.

"In part, the whole notion of the home hi-fi system for audio listening is gone." explains Gardner. "Stereo systems were cool when I was in high school. But now everything is about convenience, accessibility and portability."

This is certainly true, but isn't it also the case that the music industry hasn't been able to sell multichannel music because listeners don't feel that it's appreciably better than what they hear in stereo? Gardner believes that this argument has weight, too: "Stereo reproduction is essential to music enjoyment because it gives the sense of spaciousness. of having the music surround you. But going beyond stereo to having detailed directional control of musical sounds is not as important. because music by its nature tends to fuse into a perceptual whole."

Although some artists have chosen to release albums in surround sound (and others have been re-released in this format), the fact that both DVD-Audio and Super Audio CD failed to gain any traction in the market tells you that such releases are unlikely to become more common in the future. What's more, if you are going to produce music for multichannel systems. you need to be aware that, when it comes to mixing, it's a whole different ball game.

"I've heard really great surround mixes, but most surround mixes are simply stereo mixes with a little something thrown to the rear speakers, barely different from the original stereo mix," notes Gardner. "You really have to produce with surround in mind."

Robert Henke, aka Monolake, is an artist with a keen interest in surround sound, but even he hasn't released any music in the format "Not enough people have listening conditions that support surround," he reckons. "And for 99% of all listening situations. stereo is totally fine."

However. he feels that, when it comes to playing live, going beyond stereo really adds something. Robert says the response he's had has been "overwhelming" and that many attendees "felt they experienced something quite special".

"Surround is 'better' for my music. because I like the speakers to disappear," Henke explains. "I regard my work as 'sculpturing time' and I ideally want the result of this to feel like I am placing sonic objects in a space. I am very much concerned with questions of space and I want to be able to extend a physical space with sound to become a much larger audible space. Or I want to be able to convincingly move sonic objects through this space.

"Another important aspect is that I love density and it is simply possible to add more subtle variation and more layers of sound if those layers are played back with more than two channels. There is just more capacity to transmit information and our ears are perfectly fine with decoding these signals if they come from different locations."

Henke is an Ableton Live user, but because the software doesn't have 'proper' surround sound support, he's been forced to use workarounds for his live surround experiments. Until recently, a second laptop running Max and an ambisonics patch was used to pan ten inputs out to eight speakers, but he's since found a simpler yet more flexible solution.

"I use the Max for Live API and a Max for Live audio device to actually control sends, distance, and reverb in Live in real-time," Robert tells us. "So, all is done now within a single laptop. I plan to make the panning patcher/device public at some point. but it is still under development and I am not considering it as 'releasable'."

Henke is clearly keen to continue his explorations into 3D sound. and this has led him to losono's wave field synthesis technology, which uses between five and 500 speakers. This should not be confused with traditional surround sound systems as it uses the speakers to create the illusion of sounds in specific places, a bit like an audio hologram. This enables an entire audience to experience the 3D audio effect - not just those in the 'sweet spot'. Sounds can even be positioned next to or in-between audience members and made to move through the listening environment.

To work properly, Henke says the technology needs to be employed in a "good-sounding, damped room". but when the conditions are right. he reckons it has the potential"to reach a spatial resolution and depth that is way beyond what you can do with, say, 5.1." He offers further explanation: "It is absolutely possible to place. say, 3D virtual sound sources In a soundfield, and you can locate where they are. This is quite stunning. Also, it is possible to place sound sources 'in front' of the speakers, just like placing visual objects in front of the screen in 3D cinema."

This is all fine for art installations and dedicated concert setups, but a little impractical for home use. What if you want to experiment with 3D sound on your existing setup, without any additional speakers? There are options, including Wave Arts' own Panorama plug-in. This produces 'virtual' 3D sound and its results are best heard on headphones - not necessarily a bad thing, considering the way many listen to music now. Bill Gardner explains how it works.

"Let's start with the monophonic case - that is. building an auditory scene with a set of monophonic inputs. Each Input is spatiallsed by filtering with a pair of head-related transfer functions CHRTFs) that simulate how sound is transformed when propagating from a point in space to the ears of a listener. Basically, the sound arrives earlier and is louder in the ear closer to the source. In addition, there is complicated tonal equalization caused by the external [parts of the] ears. The gains. delays, and equalization change as a function of the position of the source. All of that is encapsulated in the HRTF filters.

"Panorama also simulates the air propagation as a delay, and simulates the early room reflections from the floor, walls and ceiling by modelling these as additional sources at reflected positions. The absorption of the walls is simulated as additional filtering. Finally, the diffuse reverberation of the room is simulated using a reverberator.

"Stereo sources are handled by spatializing the left and right channels independently, as if there was a pair of virtual speakers In the space. Panorama lets you set the center point and stereo width of the pair."

Even Gardner admits that this kind of technology has "niche uses", but it does provide further evidence that, although surround sound may not have caught on in a big way (and arguably never will), options for going beyond stereo still exist. And if there is a serious musical future for multichannel systems, it could well be in the live sector. giving musicians more creative options and the audience an altogether more encompassing experience.