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The theatre organ is an instrument which works in the same way as a pipe organ, the difference being that the pipes in a theatre organ are made to sound like instruments in an orchestra.
The organ is played from a "horseshoe" shaped console.

These organs were developed between around 1910 till around 1920`s. They were installed in movie palaces to provide music at a cheaper cost than the orchestra.
There sound is very effective.
For a closer idea of these organs and there sounds, were you can hear one and see one visit
This is a video of 2 of the worlds leading theatre organists
by Ross McNeillie October 14, 2007