What changes pitch on brass instruments?

For small intervals, there's usually a system of valves to alter the length of the resonating column of air and thus changing the pitch. For larger intervals, the player changes the shape of their lips in a specific way to create overtones. In some rarer cases, one hand may be inserted in the bell to lower the pitch by a semitone (see French horn, bukkehorn) or fingerholes used instead of valves (bukkehorn, zinck, serpent).