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Volume 123, Issue 3, March 2008
- MUSIC AND MUSICAL INSTRUMENTS 
123(2008); http://dx.doi.org/10.1121/1.2828062View Description Hide Description
In this investigation, three different swell systems known in pipe organs, the swell box, the crescendo wheel, and the historic wind swell were measured and compared to each other. The dynamic range of the crescendo wheel was found to be most effective, and for frequencies near the increase in sound pressure level could be up to between the softest and the loudest adjustment. The maximum dynamic range for the wind swell and the swell box were found to be in the same frequency range. With its step-wise crescendo procedure, the crescendo wheel simulates the type of orchestracrescendo which is reached by successively adding further musical instruments. In contrast, the swell box and the wind swell produce a crescendo effect similar to the crescendo in which individual musical instruments perform a dynamic movement. This type of crescendo requires a continuous level increase but allows a smaller dynamic range. The disappearance of the wind swell is not surprising because it offers no advantage over the swell box, while being restricted to stops with free reeds.