A similar display was necessary to draw out or push back the registers, some of which were beyond the player's reach.

In short, an assistant was necessary, in fact several assistants in playing large organs like those at Harlem or Arnheim in Holland.

It was almost impossible to modify the combinations of stops.
All nuances, save the abrupt change from strong to soft and vice versa, were impossible.
It remained for Cavaille-Coll to change all this and open up new fields of usefulness for the organ.

He introduced in France keyboards worthy of the name, and he gave to the higher notes, through his invention of harmonic stops, a brilliancy they had lacked.

He invented wonderful combinations which allow the organist to change his combinations and to vary the tone, without the aid of an assistant and without leaving the keyboard.