Mailbag: “Material Things”

January 8, 2009

Dear Michael,

Being a relative neophyte in the construction of pipe organs, having never been inside one to see the actual make-up of such things as trackers and wind chests, you can imagine that there have to be a lot of questions: materials spring to mind. Just out of curiosity, could one of your experts tell us how pipes would sound if made of lead crystal, pvc pipe or cast iron? The latter two are brought to my mind by Peter Schickele’s left-handed sewerflute.

Peter

 

Peter,

The composition of the substance from which pipes are made has an impact on organ tone. Pipes with a high tin content are brighter, with more harmonic ‘color’ than pipes with a higher degree of lead. Indeed, in some organs, the percentage of lead in the pipe metal is very near 99%, but the sheets are hammered, a process that causes a realignment of the crystaline structures of the metal and gives the lead a firmer substance (preventing droop).
Wooden pipes demonstrate different tonal properties than metal ones.
At some pitch levels the differences are minimal and some builders use aluminum for very long, low bass pipes (16’ pitch level) which is less costly, and more easily moved for construction.
The Contra Violone at the Riverside Church in New York City includes a length of flexable tubing to connect the speaking element (toe and mouth) with the main body of the metal resonator in order to accommodate its placement in a crowded chamber…it purrs beautifully.
There’s not advantage to cast iron because it is much more difficult to manipulate, and while PVC pipe is used by many builders as a wind conductor between the blower and reservoirs, its not used for speaking pipes.

Minnesota organ builder Charles Hendrickson provided this further information about pipe materials:
One must always remember that it is the air inside the pipe that is vibrating and creating sound. The air is forced into standing waves inside the pipe by being confined by the walls of the pipe. The pipe material contributes a small amount of influence on the sound, but is not responsible for the sound. Any material which will confine the air to a particular shape and volume will allow the air to be excited and forced into sounding. In a vacuum, a pipe would make no sound regardless of the material it is made of - with no air it will not oscillate. It is a combination of the air vibrating and the influence of the walls of the pipe (mass, density, rigidity, thickness, etc.) on that vibrating air. Successful pipes (all with vibrating air) have been made of tin, lead, aluminum, steel, ivory, pine, oak, mahogany, poplar and hundreds of other woods including plywood, plastic, paper, and the list could be endless until all materials have been tried. I know of no rigid material that would not make a suitable material for a pipe, but some would not be musically interesting, while others would be heavenly. It is the air that is vibrating!
Charles Hendrickson

Anyone want to add to this?

jmb

 

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