Mobile mirror to observe your own playing

It is hard to see yourself playing the upright bass. The viewing angle makes it is impossible to see if the bow goes over the strings in the right angle, if your posture is OK, etcetera. This is the solution I have found. Music stand + baby mirror + clothespins (the mirror is about 20 euro new, but an old one with a crack will do fine). Because the mirror is convex, it gives a good overview.
Use a simple musicstand to attach it to, and you have your mobile mirror.