So simple: Add a strong magnet to a pencil, coat it in rubber and what you have is a pen, that you basically can throw at your music stand to make it stick. It can even hold a few pages of sheet music and, thanks to the rubber coating, is quite silent when attaching to the stand. It works with any standard graphite pencil. I have two for my music, one on my fridge and a couple more are currently distributing themselves through the house.