Accessory weights and kits for brass instruments to reduce sympathetic vibration of a brass instrument having an instrument neck directed towards the instrument at a first end and connected to a mouthpiece at a second end; wherein the connection of the mouthpiece to the neck second end can be by a friction fit of a cork sleeve having a collar fixed to an outer surface of the neck second end; and a weight connected to the neck second end also by a friction fit to cork sleeve, wherein sympathetic vibration of a brass instrument is reduced while in use by between 10 and 50 percent.