Originally posted by Mark2100 You have to have at least an "A" lens on the camera, and the camera's flash set to HS. If it's dark, you'll have to be in "M" mode, or with more light, (where the shutter speed would be over 1/180, you can shoot in any mode except X and B.
Right, except the OP was implying using the flash in wireless mode with High-Speed Sync. This has been discussed before. With the K10D/K20D, the ONLY way to use HSS with an off-camera flash unit (wirelessly), is to have a second, camera-mounted AF540 (or, AF360/Sigma 530/Metz 58, etc.).
If you're going to be in a bar it's going to be awful dark anyway. It's doubtful HSS would even be necessary to achieve what he wants. Usually HSS is more useful if you need fill flash in bright sunlight, or perhaps if you need to use flash during action photography.
There have been some recent threads on concert photography that had some pretty good advice, regarding equipment and methods, you might try a search for those. Good luck!