AKG C 519 Clip-On Microphone
These mics are purpose-designed to clip onto brass and woodwind instruments. They are much more convenient than traditional mics on stands, and also give a more consistent sound, as the mic capsule stays in the perfect position even when the player moves around.
The clip has a very positive action, so it definitely won't fall off, but rubber pads inside the jaws ensure that it won't mark or damage the instrument in any way. The mic has a double gooseneck which allows for very precise positioning. The mic capsule gives great sound quality and can cope with extremely high sound levels.