I've been using this pencil for some time now, and I wouldn't go without it ever again. As long as your music stand is metal, this is the best option for rehearsals.
Stick it to the underside of the stand ledge and it's out of the way while you turn pages, but it's still there when you need it. You can also - in a pinch - stick it horizontally onto sheet music if it's a couple of pages thick and won't stand completely flat.
The pencil itself is good quality, and the eraser doesn't smudge.