as much as is practical & safe: use dim, subdued lighting. as much darkness as possible. deepest shadows up high toward the ceiling and down the walls, to make the room itself feel very close, as if wrapped around the listener. to illuminate the stage/artist, use only small point sources down low, around the performer. i use a bunch of warm white battery-powered LED candles and LED strings; they’re super soothing.
if there are visuals, set the projector brightness low, with muted video colors; nothing bright. consider nature scenes or abstract visuals, so that if folks want to look at anything in particular, the video doesn’t demand all their attention, or is too distracting.
comfortable places to sit, sprawl, stand, perch, lie down: options for each.
if you do want to address the audience beforehand, phrase it as a laid-back invitation, rather than a request. maybe something like, “if you end up just closing your eyes and zoning out, that’s totally okay.” and so on.
the audience will have varying levels of attention and open eyes throughout the performance. but by giving them options up front; speaking in advance, letting them choose and move through environments, visuals, physical spaces…you give them the opportunity to find what works for them moment-to-moment, to be more aware so that they can then more easily drop into that place of deep listening.