阅读理解　　　 Composers today use a wider variety of sounds than ever before, including many 　　　 that were once considered undesirable noises. Composer Edgard Varese (1883-1965) 　　　 called thus the "liberation of sound...the right to make music with any and all sounds." 　　　 Electronic music, for example―made with the aid of computers, synthesizers, and (5) electronic instruments―may include sounds that in the past would not have been 　　　 consdered musical Environmental sounds, such as thunder, and electronically generated 　　　 hisses and blips can be recorded, manipulated, and then incorporated into a musical 　　　 composition. But composers also draw novel sounds from voices and nonelectronic 　　　 instruments. Singers may be asked to scream, laugh, groan, sneeze, or to sing phonetic (10) sounds rather than words. Wind and string players may lap or scrape their instruments. 　　　 A brass or woodwind player may hum while playing, to produce two pitches at once; a 　　　 pianist may reach inside the piano to pluck a string and then run a metal blade along it. In 　　　 the music of the Western world, the greatest expansion and experimentation have involved 　　　 percussion instruments, which outnumber strings and winds in many recent compositions. (15) Traditional percussion instruments are struck with new types of beaters; and instruments 　　　 that used to be couriered unconvennonal in Western music―tom-toms, bongos, 　　　 slapsticks, maracas―are widelv used. 　　　 In the search for novel sounds, increased use has been made in Western music of 　　　 Microtones. Non-Western music typically divides and interval between two pitches more (20) finely than Western music does, thereby producing a greter number of distinct tones, 　　　 or micro tones, within the same interval. Composers such as Krzysztof Pmderecki create 　　　 sound that borders on electronic noise through tone clusters―closely spaced tones played 　　　 together and heard as a mass, block, or band of sound. The directional aspect of sound has 　　　 taken on new importance as well Loudspeakers or groups of instruments may be placed (25) at opposite ends of the stage, in the balcony, or at the back and sides of the auditorium. 　　　 Because standard music notation makes no provision for many of these innovations, 　　　 recent music scores may contain graphlike diagrams, new note shapes and symbols, and 　　　 novel ways of arranging notation on the page.