Most artists would be pretty pissed off if the audience slept through one of their performances. Luke Jerram and Dan Jones, however, actively encourage it. This is because they compose music which is scientifically designed to promote pleasant dreams... And the stage on which they perform it... is the sky.
Riding in hot air balloons with specially fitted PA systems, they drift over city centres in the early hours of the morning (the time when most people are in an REM-sleep state) and broadcast their dream-music to the sleeping populace below. This Sky Orchestra (which was inspired by the sound of muezzins' calls to prayer that Jerram hear while on holiday in Tunisia) has had two outings so far. One last year, over Bristol (pdf), and the other, a fortnight ago, over Birmingham. (The Birmingham fly-over was done as part of that city's annual performance art festival, Fierce. This leads me to hope that it might be commissioned for some future Sydney Festival. It would make an interesting change from looking up to see the usual orgy of pyrotechnics that seem to accompany any "event" in the Emerald City.)
To give you an idea of what it all sounds like, here's an audio sample from their press kit (there's also a video that can be downloaded from here). To be honest, it seems like bog standard ambient music to me, but then... I was awake when I listened to it. If you're planning to fall asleep at the computer today, it might be the perfect accompaniment. Download and doze.