Lou Skinner’s Analysis of Profiles and Trim

Linear dimensions

Lou’s analysis of profile — that is, the front-to-back dimensions of the blades (the “Bahn,” or pathway for vibrations) was based on the premise that parallel fibers transmit vibrations, while pyramidded fibers inhibit transmission. The reed begins its vibrations at the tip. If the profile is completely parallel, with a uniform thickness from collar to tip, it may take a substantial amount of air pressure to start the reed, but once the vibrations are started at the tip they will carry along the entire length of the blade, back to the collar. If you trim the tip area thin on such a parallel-profiled blade, the reed will start more easily, and the vibrations will continue to carry back along the entire length of the blade. Lou said that such a reed, with a full vibrating length, made a “dark” sound. By contrast, if the profile is completely tapered, the vibrations started at the tip will gradually die out as they encounter pyramidded fibers. Lou said that such a reed, with shorter vibrating fibers, made a “bright” sound. He described an analogy to the strings of a cello. An A played on the open A string of a cello produces a “darker” sound (in Lou’s parlance) than the same A played on the D string, because the vibrating length of the A string is longer than the vibrating length of the stopped D string.

Lateral dimensions — Color Palette

Lou’s analysis of blade thickness also included concepts of lateral, or side-to-side, dimensions. That is, how did the blade thickness change from center-line to the edges? The analysis was based on the premise that the blade could be divided into three general areas from center-line to edge, offering a “palette of tone colors”: the “highs”; the “mid-range” areas, and the “lows” (Photo 1). The center-line area, from tip to collar, produces the high partials of the reed’s crow. The mid-range areas, along the sides of the center-line, produce the “mid-range” partials of the crow. And the wings produce the low partials. The low partials provide “reediness”; mid-ranges contribute interest to the sound; and the highs give stability and focus. The blades are trimmed (with knife or file) to produce a mix of high, mid-range, and low partials that produces the general tone color that the reed-maker intends for a particular reed. For example, if the wings are left relatively thick, the tip aperture will be more open, the low partials will be free to vibrate, and the resultant bassoon sound will be very vibrant (Photo 2). If the wings are thinned somewhat, the aperture will become slightly “bowed,” and these areas will be more easily collapsed, dampening the lower partials somewhat and making the resultant sound on the bassoon less “reedy” and more focused (Photo 3). If the wings are trimmed very thin, the aperture will be even more “bowed,” and these areas will be very easily collapsed (Photo 4). A reed trimmed in this fashion will produce a sound on the bassoon that Lou called “dumpf” (German for “muffled” or “dampened”), because the low partials are not present.

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