The Caribbean Steel Pan: Tuning and Mode Studies
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sections to vibrate. The nature of the coupling between sections has been the subject of considerable interest to researchers in the field.1 Inasmuch as the entire pan represents a highly nonlinear system, the tone quality also varies significantly with excitation amplitude. Tuning To appreciate the tuning process, it is important to understand several characteristics of the steel instruments that pose challenges to the tuning procedure. First, since the pans are usually crafted from commercial, 55-gallon, steel oil drums, there is little control over the quality of the material from a metallurgical standpoint. As a result, imperfections in the grain structure of the sheet metal used can interfere with the instrument's ability to respond to vibrations. Second, tempering the instrument is an imprecise process. Heating temperature and
duration vary from instrument to instrument, and the resulting variations in stiffness cause variations in vibrational characteristics. Third, the skirt of the barrel is not made of the same material or steel gauge as the playing surface. These fluctuations cause the skirt to produce "metal tones" which may interfere with notes on the playing surface. Finally, note coupling, which contributes richness to the sound, contributes to tuning difficulties. Before describing tuning methods in detail, a brief characterization of the construction process is in order. The flat surface of the drum is "sunk" with a series of hammers, starting with a 6-lb sledge hammer, and continuing with hammers of decreasing weight until the surface resembles a portion of a spherical bowl. The depth of the bowl is determined by the desired pitch range for the pan, with the higher pitched instruments receiving the greater depth. Consequently, a typical family of nine instruments ranges from a depth of 8.5 in. with a 5-in. skirt to the entire length of the barrel with a sink of 4.5 in. The sinking is followed by the process of laying out the playing surface, as well as the indention of the note boundaries with a small metal punch. The drum skirt is then cut to the desired length, and the note areas are slightly bubbled up with a hammer. Now the instrument is ready for tempering by heating. The metallurgical properties of the steel are modified and strengthened. The drum is placed, faced down, over an open flame and heated to about 600°F (315°C). It is then removed and left to air cool, whereupon it is cleaned. In the preparation stage, the notes are flattened and then tightened around the
Bass
1.5/ Figure 1. Representative note arrangement for several pans.
MRS BULLETIN/MARCH 1995
The Caribbean Steel Pan: Tuning and Mode Studies
CI (Octave)
I
per partial located at the top and bottom of the section. Hammering from the top in the octave area will raise the pitch of the octave; hammering from below will lower the octave. Octave tuning will influence the pitch of the fundamental, which will have to be retuned by hammering in the center of the note area from below to sharpen the note or by striking the "de
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