By taping thirteen rulers to a desk, each with a different amount of overhang, we have a rudimentary musical (?!?!?!?) instrument. So, how much overhang is necessary, how do we do it, and why? Well...

If there's one piece of science that every kid knows, it's that twanging a ruler on the edge of the desk makes a noise, and by changing the amount of overhang will change the pitch. Give anyone a new ruler, and the first thing they'll do is twang it, to see how it sounds. This is an interesting fact of life.

To intellectualise this pastime we can say that we are discovering the relationship between wavelength and frequency (the longer the ruler overhang, the lowest the frequency of the note), and that we're listening for the timbre (pronounced tam-ber), which indicates the character of an individual sound, and is why a violin and piano sound different when playing the same note. This is less interesting fact of life.

Step 1: Prepare the rules

We start by determining the length of each overhang. By knowing how much is needed for the lowest note, C in our case, we can calculate the others mathematically. Finding the lowest note is done in typical school kid fashion by experimenting, unless you have a keyboard, guitar, or other musical instrument and an extra pair of hands, er, to hand.

You will notice that some lengths do not produce notes at all. Very short distances just produce a click, while very long ones make no sound at all. To make a complete octave, the overhang of the lowest note will need to be twice as long as the shortest (highest note), so if the rules you're using only make sounds between 5cm and 8cm you won't get a full octave.

TIP: Hold the rule to the desk as tightly as possible to produce the best audio fidelity (read: twang) possible.
How totally wonderful!
I tried this with a couple of rulers and I think that the length is multiplied by 4 to be an octave lower.
I think it's proper that you used "make" to hold it down to the table.
which c does it start at?
i would imagine you could maybe get some plywood or something, sandwich then inside, and make a ruler kalimba.
awesome, *cough*
I just saw all the Make Magazines and started salavating!!
this is pretty nice.. you have a lot of time on your hands but i could see this being very useful with a creative mind.. mad ups to you
These make magazines deserve better luck.....
Super thorough! I love that you describe all of the science behind everything!
no video? you're killing me
go to the third step, the videos there
*cough*<br/><br/><a rel="nofollow" href="http://uk.youtube.com/watch?v=jFG9uR9Q_L4">Rule Organ video</a><br/>
So... Embed it in the instructable already! Then you'll get my "+". ;-)
Done! Anything else you want? A moon on a stick :) :) p.s. to others, uk.youtube domains don't work with embeded videos, you have to use the US site.
Nah, I'll settle for the "Make Rules!" you have pictured above.
This is a phenomenal example of instruments of its type. I have only ever made a 13-note single octave, but my family and I are collecting different types of materials of differing lengths to accomplish something more permanent. I have found that metal rulers have more "brightness" in a piano sense, and more resonance overall, than the plastic shown here, but I am biased to metal, as I aspire to make the thing an "acoustic-magnetic" organ. Kudos on the clarity of design!
I have always really enjoyed playing the ruler, although I play more of a "slide ruler" style-- fretless if you will. My favorite are the 1/2" wide steel machinists rules. They make a great sound.

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