stop. The number is
unlimited.

The Romans made organs which must have been simple from the musical
standpoint, though they were complicated in their mechanical
construction. They were called hydraulic organs. The employment of water
in a wind instrument has greatly perplexed the commentators.
Cavaille-Coll studied the question and solved the problem by
demonstrating that the water compressed the air. This system was
ingenious but imperfect, since it was applicable only to the most
primitive instruments. The keys, it seems, were very large, and were
struck by blows of the fist.

Let us leave erudition for art and primitive for perfected instruments.
By the time of Sebastian Bach and Rameau the organ had taken on its
grandiose character. The stops had multiplied and the organist _called_
them by means of registers which he drew out or pushed back at will. In
order to give greater resources, the builder multiplied the keyboards.
Pedals were introduced to help out the keyboards. At that time Germany
alone had pedals worthy of the name and worth while in playing an
interesting bass part. In France and elsewhere the rudimentary pedals
were only used for certain fundamental notes or in prolonged _tenutos_.
No one outside of Germany could play Sebastian Bach's compositions.

Playing on the old instruments was fatiguing and uncomfortable. The
touch was heavy and, when one used both the pedals and the keyboards, a
real display of strength was necessary. 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. Even before his day a scheme had been devised of enclosing
certain stops in a box protected by shutters which a pedal opened and
closed at will; this pe