A tripod is important if you can get away with using one. I shot some film of Chuck Berry a few years ago performing at night and it was very hard even with ISO 400 and no tripod. Solutions: Fast (bust ghastly expensive) ED glass telephotos and zooms, at least ISO 800 film or better ISO 1600, and a tripod/monopod. Being discrete is necessary today too with everyone paranoid about cameras and copyrights - these are sort of conflicting requirements.