A training device for use by a player with a brass instrument having a tubular mouthpiece receiver with an opening in one end and a mouthpiece having an elongated shank at one end for insertion through the opening into the receiver. The device has a substantially planar shield having an upper side and an underside and an aperture formed therethrough and at least two elongate, flexible and resilient prongs extending generally perpendicularly from the periphery of the aperture along the underside of the shield. The training device is inserted prongs first into the receiver until a gap is defined between the underside of the shield and the one end of the receiver. The mouthpiece shank is then inserted through the aperture for concentric positioning within the receiver with the prongs spacing the shank from the inner walls of the receiver.