A portion of the register unit is visible at the lower right, which is a rather complicated unit containing both primary and secondary (lever or rocker type) valves. The small wooden dowels sticking up at the front of the unit are the guide stem portion of the very sensitive primary valves.

The treble end of the reiterating xylophone is visible at the lower left, with the three ranks of wooden pipework rising up in the rear. The large pneumatic motor fastened to the end of the xylophone operates the swell shutters, which are mounted in the roof of the PianOrchestra.