A unison gauge for indicating levelness of a string set of a grand piano
is described. The gauge has a contact block adjustably engageable with
the lowermost tangential aspect of the string set. Battery powered
indicators provide an indication for each string. With the piano action
withdrawn from the piano case, the base of the device rests on the key
bed below the piano hammer strike area of the string set and holds the
contact block mounted thereon on an extendable mast. The contacts of the
contact block are in a plane parallel to the key bed. The contact block
is under slight spring tension when engaged with a string set being
monitored and, upon compression of the spring readily slides along the
key bed to the next string set. A method of use of the unison gauge is
also provided.