THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

18.9 Strings 527The difference between the construction of a banjo and other string instrumentsis that its body consists of a skin membrane stretched over one end of a truncatedcylinder, thus making the body drumlike. The other end of the cylinder is open. Thebridge is supported by the stretched skin and it couples the strings to the stretchedmembrane, which, in turn, provides a large resonant area that is coupled to theair. Four long strings and a short string are stretched over the bridge between thetailpiece and the fingerboard. The relatively long neck is fretted; the short string isreferred to as the melody string. A more modern version called the tenor banjo isequipped with four strings of equal length, and it has supplanted the older modelwith the one short string. The four open strings are tuned to C 3 ,G 3 ,D 4 , and A 4 .This instrument can be played by either plucking the strings with the fingers orwith a pick or plectrum that can be made of a flat piece of tortoise shell. The noteof a string and hence the resonant frequency can be varied by pressing it againstthe frets. The spacing between a pair of adjacent frets corresponds to a differenceof one semitone. The overall length of a banjo is approximately 86 cm.Over the past three decades, Europeans and Americans have become familiarwith structured musical compositions called ragas through concert performancesby Ravi Shankar who performed them on the sitar which is northern India’s predominantstring instrument. The sitar’s seven main strings are tuned in fourths,fifths, and octaves to approximately F # 3 , C# 2 , G# 2 , G# 3 , C# 3 , C# 4 , and C# 5. In additionthere are 11 sympathetic strings tuned to the notes of the raga. The inharmonicitiesare quite small; the high-curved frets permit the player to execute with vibrato andglissando. The curved bridge allows for both amplitude and frequency modulationfrom the rolling and sliding of the string.The harpsichord (or cembalo) and its older cousin, the clavichord, both of whichresemble shrunken baby grand pianos (the clavichord is more boxlike in configuration),trace their common origin as far back as the twelfth century. The harpsichordwas the mainstay of chamber music during the baroque and classical period untilthe advent of the more versatile and louder pianoforte, the immediate precursorof the modern piano. Because so many excellent examples exist to this day, theart of constructing harpsichords have been revived so that modern audiences cantoday enjoy the music that have been composed expressly for this medium. Duringthe twentieth century, a number of excellent performers revived audience interestin the instrument and the works written for it, among them the great WandaLandowska and later on Igor Kipnis (the son of the great Ukrainian operatic basso,Alexander Kipnis).Figure 18.16(a) illustrates the structure of a harpsichord, which consists of a largenumber of steel strings stretched over a rather triangular steel frame. The keyboardranges about 4 1 / 2 octaves from A 1 to F 6 , but different versions of harpsichordshave been built to cover both larger and smaller ranges. The strings are excited bybeing plucked by a key-actuated mechanism shown in Figure 18.16(b). The keyis coupled through a level system to a short plectrum of leather, fiber, or tortoiseshell that plucks the string which deflects to let the plectrum slip past. When thekey is released, the plectrum, which is attached to a short spring-loaded level, slipsback under the string. A damping pad also mounted on the jack stops the sound.