g, inserted in the middle of the key action. The exertion of
depressing the key is now reduced to the small amount of force required
to open a valve, half an inch in width, which admits wind to the
bellows. The bellows, being expanded by the wind, pulls down the
pallet in the wind-chest; the bellows does all the hard work. The
drawing on the next page, which shows the lever as improved by the
eminent English organ-builder, Henry Willis, shows the cycle of
operation.

When either the finger or foot is pressed upon a key connected with
_k_, the outer end of the back-fall _gg_ is pulled down, which opens
the pallet _p_. The compressed air in _a_ then rushes through the
groove _bb_ into the bellows _cc_, which rises and lifts with it all
the action attached to it by _l_. As the top of the bellows _cc_
rises, it lifts up the throttle-valve _d_ (regulated by the wire _m_)
which prevents the ingress of any more compressed air by _bb_. But the
action of the key on _gg_, which opened the pallet _p_, also allowed
the double-acting waste-valve _e_ to close, and the tape _f_ hangs
loose. The compressed air, therefore, as it is admitted through _bb_
cannot escape, but on the other hand when the key releases the outer
end of _g_, and lets it rise up again, the tape _f_ becomes tightened
and opens the waste-valve, the bellows _cc_ then drops into its closed
position.

[Illustration: Fig. 3. The Pneumatic Lever]

The organ touch could now be made as light as that of a pianoforte,
much lighter than ever before.

This epoch-making invention, introduced in 1832, rendered possible
extraordinary developments. It was at first strangely ignored and
opposed. The English organ-builders refused to take it up. Barker was
at length driven to France, where, in the person of Aristide
Cavaille-Coll, he found a more far-seeing man.

After Cavaille-Coll had fully demonstrated the practical value of
Barker's invention, Willis and others joined in its development, and
they contemporaneously overcame all difficulties and brought the
pneumatic action into general favor.

This process, of course, took time, and up to about fifty years ago
pneumatic action was found only in a few organs of large calibre.

The recent revolution in organ building and in organ tone, of which
this book treats, was founded upon the pneumatic and electro-pneumatic
actions invented by Barker.[2]

It is safe to say that the art of organ building has advanced mor