Patent ID: 7667117

Claim:
A musical instrument piston valve receivable in a valve casing with at least one valve guide key slot, the piston valve comprising: a valve barrel including at least one slot of a predetermined width; a piston extending from the valve barrel and including one or more ports; the valve barrel and the piston monolithic in construction; and a rotatably adjustable valve guide within the valve barrel, the rotatably adjustable valve guide including: a first plate including at least a first key received in said valve barrel slot and having a width the same as or approximately the same as the predefined width of the valve barrel slot; a second plate rotatable with respect to the first plate, the second plate having at least a second key received in said valve barrel slot and having a width less than the predefined width of the valve barrel slot, and one of said first and second keys received in said valve casing valve guide key slot.