This is Stephen Paul Kowalyshyn in the voicing room working on the mixture for Opus 123. He's the inventor of the Kowalyshyn Servopneumatic Lever, a key action assist device used in many of Fisk's larger organs:

Here's Opus 123 which was being set up in the erecting room:

Fisk makes very detailed models of their organs. Here's Opus 100 from the Meyerson in Dallas:

This is a separate model of the back of Opus 100:

Here's the model for Opus 101: