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Diagram of the Procedure!
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".
MATERIALS:
WOOD
GUTTER PIPE
STRING
2 EYE HOOKS
RUBBER BANDS
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. |