Abstract: A pair of arms extending from a closed looped end of the frame are flexed toward each other and have apertures at their free ends to receive a spacer pin having opposite ends removably engaged in such apertures. The pin has lateral abutment at these apertures to provide selected spacing of the arms and maintain them out of contact with a reed extending from the looped end. The base end of the reed seats in a shallow groove and is clamped for longitudinal and lateral adjustment by a removable clamp plate.