I'm building a mobile, open source, midi controlled pipe organ. I'm calling it the Anywhere Organ. This site is here to document my progress, acknowledge all the awesome people who are helping make it happen, and spread what I've learned in making this colossal instrument.
I spent the afternoon dimensioning my new set of pipes to start mocking them up in CAD. It was really interesting putting together the data and seeing such a clear trend emerge. See that pretty parabola in blue down there? That curve more or less represents the volume of the air column in each pipe as it goes up in pitch. The less space there is for the air to pass through the closer the pattern of interference of air knocking around inside and the pipe produces a higher frequency sound as a result.
Wikipedia, which is my source for sounding well informed, has this handy formula to offer:
Essentially it means that the pitch of a pipe (F) is equal to the speed of sound (V) over twice the pipe length (L). Let’s work this out.
A small C note should be 130.81hz in an ideal universe. From my chart the C I’ve got is 58.5 inches long or 4.875 feet. That means my frequency equals 1130 fps / 2(4.875) or 116hz. That’s quite a bit off. It seems like my pipes aren’t tuned to precise eight foot pitch. Somehow my C2 is somewhere between A2 and B2 on the concert pitch scale. Further investigation is necessary. I might have to make sure there are options to change the tuning of the instrument if it’s interacting with other instruments or recorded tracks. It should be a pretty simple MIDI transpose.
For the moment I’m simply stoked I have pipes to play with.