I shoot live concerts, so I don’t really worry about what ISO I’m shooting at. Modern camera bodies are so good at noise reduction and getting a really clean image at stupid-high ISOs these days, it really isn’t that big a deal. Note - I’m not saying you should go out and shoot at ISO 150,000. Shoot as low as you can with getting a clean image, even if it is slightly underexposed. You can easily do a salvage job in post. Beats not getting any shots because “it was too dark” - especially on a paid gig.
Hey! What is the genre of music? Folksy singer/songwriter? Black Metal? 1980s Hair Metal? I think a lot of what your artist’s genre is and what type of look you’re going for as an end image will largely dictate what sort of techniques as well as which gear to bring to get your intended shot.