Public musical instrument installation-- help!

[Natalia Olbinski]

Hello!

I am working on a conceptual project, a musical park, as a proposal for an unused space in an up-and-coming cultural district of Warsaw, Poland. The space is surrounded by a science center, music academy, and The Chopin Museum, thus thematically a musical "playground" fits in very well. Unfortunately the deadline for the proposal is in exactly one month from today, so I am pressed for time. One of the ideas was to a pipe organ, which would be played by jumping on or squeezing hemispherical rubber elements placed in the ground and at hand height. Another instrument is a rotating metal harp.

I have no experience designing instruments and would love a professional opinion. I would like to have the proposal for it as accurate
as possible, especially when it comes to the design specifications of the instruments. So, general questions are as follows:
Are these at all feasible concepts? Are there things that I have neglected to consider? As this is a public installation and has to withstand weather conditions, how would that have an effect on the tuning?

Specific questions for instruments:

Pipe Organ: what is the best way to determine the heights and diameters of the individual pipes? Would it be detrimental to the sound to have the pipes welded together, or do they have to be separate?

Harp: Is there a rule to how large the resonating box in proportion to the size of the instrument overall? Does it need to be built in any specific way (one piece, or several pieces fastened together w/ screws?) Any help on tuning is also welcome as I am confused about it in general.

Thank you so much in advance for the advice!

[Charlie Schultz]

Hi Natalia and welcome to the forum. Please note that we require the use of real first & last names. You may PM me or one of the moderators with your correct name and we will be glad to update your registration info. As for the organ questions, hopefully one of our members with experience in that area will be by shortly. Thanks!

[Steve Senseney]

Sounds like a fun project and a fun park!

Here is a link to a video. If you like the idea, the PVC pipe is universally available.

Edit--forgot the link--

http://www.youtube.com/watch?v=0D2o8F2MOuI

[Yuri Terenyi]

Hello Natalia.
A quick rundown to the questions.
First, the harp. No, there is no hard and fast rule about the soundbox size. You'll get a sound as long as there is a reasonably-sized soundbox. How it is constructed is also quite flexible. What matters is that there is a reasonably sized resonating soundboard. Which means a flat, uninterrupted expanse of some kind of wood. Now, I could go into discussions about which woods are best, but in this case it's quite irrelevant. I would suggest a thin good-quality plywood, strenghtened with struts glued on on the inside. In fact, I have heard harps built with plywood, sounding quite decent. They weren't concert quality, but tis project is not about concerts. If you drew a sketch of what kind of thing you have in mind, that would help with more specific replies.
Now, the organ. (I also thought first of an instrument just like Steve sent a link to, except the one I saw in use had the playing surface just like in the video, but the pipes themselves were arranged in pipe-organ fashion. They curved up from behind the flat board, and went straight up.) The tuning is the most difficult one, if you want them in reasonable tune. You need to tell wnat kind of pipes you have, before any meaningful answer can be given. Tuning depends on the type of pipes (reed/flue), the lenght, conicity, if any, and inner diameter. Also, with flue pipes, whether they are open or closed. However, even knowing all this, you cannot just cut a pipe to exact lenght, and have it in tune. All organ pipes are left slightly shorter/longer than needed, and then all of them have a mechanism by wich fine tuning can be done. A good organ will have a complete tuning overhaul at least once a year, preferably once every change of seasons. To really answer more specifically, we need to know the pipes' type.
But at least one question I can answer. The welding of the pipes together will not affect the sound , either quality, or pitch.
I only just noticed that the first sketch has a note. Well, that slit in the back is the tuner. What happens is that by leaving an opening there you get the same effect as what you get from having a fingerhole on for example a recorder. You open the fingerhole, and the speaking lenght of the pipe cuts off at that point. (OK, not totally true, for the purists around here, but true to practical purposes.) With the long slit, you tune it by shortening/lenghtening the slit. Trumpet ends will not in fact make much difference to the sound itself with this arrangement, even though they do look dramatic. So if it's pipes of the kind in the drawing, you need to tell us the number and sizes available. Unless they are going to be manufactured from scratch, in which case I myself doubt it that there is enough time left for a reasonable job for this part of the project.

[Natalia Olbinski]

Wow, Yuri, thank you for your response!! And thanks Steve, for the link. I've been spending so much time looking at youtube videos of instruments like this!! I just realized I don't have a sketch of the harps up, I'll have to scan and prepare that. I'm running out the door now but will post what I had in mind later today. Thanks again for taking the time to answer.

[John Peterson]

Natalia, I love your drawings! It looks like a really fun idea. The concept of having a tuning slit in the back of the pipe and then capping the top with a trumpet like bell can definitely work. The hemispherical rubber blowers might not be a large enough air source. As drawn, the pipes would produce a short "honk," and not a sustained sound. That might be desirable, though!

There is a lot of information available (both books and on the internet) about pipe construction, and the ratios of the pitch:diameter:length:mouth aspects of different types of organ pipes. A good book to start with is "The art of organ Building, volume II" by George Ashdown Audsley. This book contains a chapter on the construction of metal pipes, and should be a big help. Also do a google search for "Organ Pipes" and you should find useful websites. I think there are youtube videos on pipe construction as well.

For your purposes, I would suggest sticking with "flue" type pipes rather than "reeds." They will be more durable and less finicky, as well as much easier to construct. (Just to be clear, in a flue pipe the sound is produced like a recorder or flute just as you have drawn in your pictures. In a reed pipe the sound is produced by a vibrating reed, as in a clarinet or saxophone.)

In a real pipe organ, as the pitch goes up and the pipes get shorter, they also decrease in diameter. They do this to maintain a uniform tone quality. You might be able to get away with making several pipes in the same diameter, controlling only the length for pitch. These pipes would not sound exactly the same. Some might sound more "hooty," and some might have a thinner sound, for example. In an art installation like this, though, this could be OK, and even desirable, adding an element of fun.

I cannot really contribute to the discussion on harp construction, except to say that wind blowing through harp strings produces wonderful eerie sounds. (Look up the "Aeolian Harp") You may be able to take advantage of this phenomenon too.

Please keep us posted. This is a very interesting project!

John

[Simon Chadwick]

For a harp, it can be any shape you like, but there are some sensible constraints. e.g. the strings lying at about 30 or 40? degrees to the soundboard, the soundbox being tapered in at least one dimension (wider soundboard in the bass), and the string lengths being at least approximately pythagorean scaled, especially in the treble to mid range.

Tuning will be a problem. Perhaps the idea I saw on a fiddle installed in a cafe mechanical orchestrion would work - the strings were weight-tensioned through levers instead of spring-tensioned through turning a tuning pin set in the frame. The weights and levers could be concealed inside the soundbox. This would also save people breaking strings by pulling too hard - the string would just give a little.

[Andy Barnhart]

Simon,

Great idea, stolen or not. The only problem that occurs to me is that wound strings would go out of tune if any winding broke, even internally (that happens on guitars without people realizing it; they just realize it is oddly flat and tighten it) or a wire string gets stretched. But I still like the idea. Other methods of keeping strings in tune have worse issues. It might help to have covers so that only an inch or so of the strings can be accessed, and some sort of outside containment so they can't be pulled to far to the side (or people will launch arrows with them).

[Natalia Olbinski]

Thank you so much for your responses, I apologize for not replying sooner. For the harp tuning I was thinking, that maybe it would just be standard with guitar tuning pegs, with a cover so that when it is out of tune, someone (a park supervisor?) would attend to it and not the general public. And Andy, it never crossed my mind that people could (and probably would) launch arrows! I am going with faith in humanity on this one and leaving longer, exposed strings. I'm not entirely certain how they would be weight tensioned, I tried searching but to no avail... thank you for the suggestion though, Simon, and perhaps you could explain a little bit more how that would work?

John, I realize that the rubber blowers would not provide a sustained tone for the organs- but I am not overly concerned about that. I'd like to keep it as simple as possible-- unless of course there is a simple mechanism by which a sustained air flow could be achieved. Mostly-- I'm worried about these instruments surviving the winter.

Thanks again for taking the time to answer my questions!

[Natalia Olbinski]

..and one more organ file

[Andy Barnhart]

I don't mean the general public, but yeah, kids pick up sticks and try to launch them when stretchable strings are in a park. Maybe liability is more rational over there. In the US, considering that sort of possibility is an unfortunate reality in public planning.

As far as Simon's weight idea, think of it like this - if you have a string staked to the ground looped over a bar above your head with a jug hanging from it, the more water you put in the jug, the higher the note you would get if you plucked the string.

[Steve Senseney]

Here is a web page with a drawing of a ancient wind chamber for a pipe organ. It is a system of multiple bellow, pumped by standing on the bellows.

http://www.die-orgelseite.de/funktionsweise_e.htm

I think you could adapt this kind of bellows for a organ. It would be great exercise for the kids. It would also make the organ a group instrument.

I remember seeing a drawing of a primitive organ where the largest pipes were opened by heavy pedals instead of "keys" like we usually think about. Large pedals might be more fun for kids as opposed to a simple modern keyboard arrangement.

[Steve Senseney]

Here is a web page with a drawing of a ancient wind chamber for a pipe organ. It is a system of multiple bellows, pumped by standing on the bellows.

http://www.die-orgelseite.de/funktionsweise_e.htm

I think you could adapt this kind of bellows for a organ. It would be great exercise for the kids. It would also make the organ a group instrument.

I remember seeing a drawing of a primitive organ where the largest pipes were opened by heavy pedals instead of "keys" like we usually think about. Large pedals might be more fun for kids as opposed to a simple modern keyboard arrangement.

[Simon Chadwick]

This hopefully shows how I imagine the lever tuning / tensioning device.

I think that the idea of manual tuning will not be a goer, unless you can provide an endowment to pay for someone to go in and tune the thing every day for the life of the installation (and even then it will be sounding awful by lunchtime if some eager kids have a go at it!)

I have shown the levers installed inside the soundbox. I would think that a steel string would not stretch much so the distance from the fulcrum to the string anchor might be OK as little as 1cm, perhaps 2cm. I have shown a guitar tuner mounted on the fulcrum so the length of the string can be adjusted to make the lever arm level. On my harps the string tension tends to be around 10-15kg force, so a weight of 1kg at the end of an arm 10 to 20cm long would provide appropriate tension, and would easily fit inside the soundbox. I also have shown a screw adjuster for the weight, to allow fine tuning of each string. Once both these screws are set on each lever, the thing should stay in tune for some time, perhaps months, without needing adjusted.

On the shape of your harp, two comments. The soundbox should be deeper both to enclose more volume and also to contain the mechanisms. Also, the top part (the "neck' or 'harmonic curve') is bent the wrong way. You want ideally every 8th string to be double the length, this is why the neck of most harps has a dip in the middle rather than a hump as you show. If you have it hump-shaped then your central strings will be rather long and the strings at top and bottom of the range will be too short and sound dull.

[Steve Senseney]

This project is really a fun concept.

For the organ, if there is a water feature in the park, you could consider the Hydraulis concept to power the air chamber for the organ.


http://en.wikipedia.org/wiki/Water_organ

[Yuri Terenyi]

For the organ, if you stick with the original rubber bulb idea, the bulbs will have to be considerably bigger than in the drawings, for this size pipes. I think a little bulb like the ones drawn won't even make a hoot, unless squeezed very fast.