I finally got sharp handheld shots at my niece's recital after a dad next to me mumbled one thing
He leaned over at intermission and said his trick is just planting both elbows on his ribs and breathing out slow before he taps the shutter. Tried it for the second half in that dim auditorium and got maybe 8 keepers out of 12 instead of my usual 1, so what else works when you can't use a flash?
A steady arm doesn't fix a sensor that's crying for light, so those "keepers" are probably just the ones where your niece happened to hold still for a split second. Bumping ISO way up on that dim room beats any elbow trick, grain and all.