The action
Current tracker action is the one designed and built by Aristide Cavaillé-Coll in 1861; being mechanical with a Barker lever for the Grand-orgue and couplers.
This Barker lever is similar to the ones at the Saint-Sulpice organ in Paris, with a specific valve system later developed, standardized and used by Cavaillé-Coll.
There is no roller at the Grand-orgue, Bombarde and Pedal; the movement’s translation is done through horizontal roads. If we believe a quote made by Callinet, the long roller boards made originally by Dupont tended to twist, which could explain why Cavaillé-Coll chose this system.
The stops action is also mechanical by iron rollers, Clairon and Cornet from Récit excepted, which are pneumatic. In order to add a Plein-jeu at the Récit, Haerpfer-Erman had to shift the Trompette’ and Clairon’ sliders, the latest being added on a side of the main windchest. The Cornet stays outside of the expressive box, at the right-hand side. The pneumatic motors of the Clairon and Cornet are located at the expressive box’s front.