Build A Water-Marimba
In the pieces: HONOR, COURAGE... COMMITMENT and BY LOVE COMPELLED... AT THE HOUR OF SHADOWS, I have asked for the creation of an instrument. This percussion instrument's construction is described loosely in the score notes.
Thanks to STORMAlly, Scott Rogers, advancing the cause of Music on the vast outreaches of the Norwegian Frontier, here now is a step-by-step procedure for creating a "Water-Marimba.”
2 EYE HOOKS
Get a piece of wood l x 3 inches, 20 inches in length.
Choice 1: Spruce
Choice 2: Rosewood
Choice 3: Cedar
The wood should be clear heart ( no knots or sap wood), vertical grain (line of the grain is parallel to the edge of the board), quarter- sawn wood (cut along the radial lines of the log). The guys down at the lumberyard will understand this kind of language. Best results are often obtained from dry wood (air or kiln dried) which has a fine, tight, even grain. Hold a prospective board at the node (about 1/5 of the total length in from the end) and rap it with your knuckle. You should be able to get a rough idea of its sound potential.
Get a 4-inch diameter gutter pipe with a T-fitting (like the ones on your house). This is what we will use to make the resonator. Since our 20-inch piece of wood should give us something in the neighborhood of an F below middle C (174.6 hz), we will need a resonator that is at least 18 and 1/4 inches long. My suggestion is that you make it 5 or 6 inches longer than that. This way, as you lower your resonator into a pail of water, the closed end of the tube will gradually approach the notes' "sweet spot" where you will obtain your most resonant sound.
PUTTING IT TOGETHER:
Measure to a point equal to 20% of the total length of the board in from each end. This is the acoustical node. Drill a hole through the sides of the board. This will be the point from which we suspend the board over the resonator.
Draw a line 3/8ths of an inch in from each nodal point. Between these two lines remove roughly 50% of the boards mass. A little less towards the nodes and a little more in the middle. Later, when you are fine-tuning your bar to a strobe you can remove more from the middle to lower the pitch or cut away a little from each end of the bar to raise the pitch.
When your bar is tuned to the desired pitch, suspend it in the T-fitting by drilling holes the same distance as the nodal points in the T-fitting. Pass the string through the T-fitting and the holes in the bar. Make sure both ends of the string come out on the same side and that they are several inches too short for you to tie them together. At this time, tie an eye-hook on to each end of the string and tension them by means of the rubber bands.
Place the T-fitting on the gutter-pipe resonator and voila! You are all set. Get a large pail full of water. Lower the resonator slowly in and out of the water while playing the bar with a medium yarn xylophone mallet.