The large Imhof & Mukle weight-driven, barrel-operated orchestrion in
the Sanfilippo Collection (previously in the Ashorne Hall Collection of
the late Graham Whitehead) has an interesting feature that effectively
allows for data compression.

Among the keys for playing the notes, percussion instruments and
automatic registers (which automatically turn various ranks of pipes
on and off), there is a pair of keys that control fast and slow
rotation of the barrel.

Two large weights hanging from cables provide power for pumping the
bellows and turning the barrel.  When a slower, softer passage occurs
in the music, a certain key actuates a braking mechanism.  This presses
felt-tipped levers gently against friction wheels on each of the two
air-brake fan shafts, slowing the mechanism to conserve precious air
and playing time on the costly barrel.  When a louder, faster passage
occurs, another barrel pin releases the brakes, permitting the
mechanism to turn at normal speed again.

With this arrangement, the longer notes in the slower sections of music
are pinned with relatively shorter staples or bridges, representing
a form of data compression from over 110 years ago.  (See p. 35 of my
book "The Golden Age of Automatic Musical Instruments" for pictures of
this mechanism.)

Art Reblitz