The pipe organ for St. Philip's Presbyterian Church is made of two elements, the wind supply and the organ itself.

The wind supply consists of a small 1 1/2 HP turbine blower which supplies air under a very low pressure (5" water column) to the four bellows. These bellows (eight feet by four feet) are located behind the organ case and work in similar ways as an old fireplace bellows. In this case they act as regulators and meter air of very specific pressure to the organ. This happens in various amounts d epending upon how the organ is being played. The maximum flow occurs only when the organ is played in an "pull out all the stops" mode and should not exceed 900 CFM. Since this air comes from the same space the organ occupies (the interior of the sanctuary) and comes out of the pipes (also located in the sanctuary) there is no impact on the building. Under normal playing the wind demand is much lower, sometimes as little as 5 CFM. When the organ is resting but turned on the flow could be as low as .5 CFM as there is a very small amount of seepage throughout the system. An average wind flow for an hour long church service is perhaps 10 CFM.

The organ itself consists of three elements that relate to air flow, the trunking, the wind boxes (called windchests) and the pipes. The windchests consist of frames that contain channels, one for each key, and toeboards that support the many pipes as well as channeling wind to them. There is also a section (called the palletbox) which contains the many valves that supply wind to the channels, each one connected to a key of the keyboard. There are eight windchests positioned throughout the organ, each holding many pipes of various sizes, the small ones high pitched, the long ones low pitched. When winded the pipes play their note in similar ways some wind instruments produces tone in an orchestra with the exception that each pipe can play only one note, consequently the many pipes (more than three thousand in the St. Philip organ).

How wind flows through the pipes determines the tone and this is where the art of voicing comes into play. The wind sheet formed by the lower lips of each pipe mouth (most of the pipes work like a flute) can be shaped in subtle ways to make the tone bright or dull and furthermore, the pressure we set the organ on over the course of four months of voicing and tuning will also determine this tone. There are many other aspects of how air flows through a pipe that falls into the "art" category but these are for a related description. The goal is to make a sound that can support the congregation when they sing the hymns and liturgy as well as a sound that can effectively accompany the choir and soloists. The sound must also be appropriate for the vast organ literature composed over the course of many centuries. We must be mindful that not only are there many centuries of organ compositions but they come from many organ cultures: English, French, German, Spanish, Italian, and of course American. The flow of wind then is a key element in this art form.

Like organs built before the electric motor, the St. Philip bellows are fitted with levers and valves that enable the blower to be turned off and the organ to be foot pumped. The air is drawn into each bellows through one way valves when the bellows pumper steps on a foot pedal that raises the bellows. As air flo ws out of this bellows into the organ the pumper moves on to the others. When the organ is used this way the whole experience becomes a human powered event, an event that an audience will perceive differently, an event that takes us back to an earlier era. We also eliminate the blower turbulence sometimes heard in the higher pitched flutes. Another reason for doing this is that the wind behavior, the way the bellows react to the changing demands of wind as music is played, becomes more musical. This is due to the mass of the levers moving and the one way check valves present.

Respectfully submitted,

Paul Fritts
Paul Fritts & Co. Organ Builders