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The title of these
etudes . . . comes from Atlas
Australis, a book of star maps printed in six
colors . . . In order to write
one of the 32 two-page pieces, I begin by placing a transparent grid over
a particular one of the 24 maps. . . . I decided to
distinguish between
the six colors, so that at times all stars might be traced, at other times
only certain of them would be.
I also made use of the I Ching, not as the book of wisdom it is, but as a means of answering questions through chance operations in relation to the number 64. Thus, having placed the transparent grid over the star map . . . I ask which stars I am to trace and how many. Numbers 1-9 give blue and green; 10-18 orange and red; 19-27 yellow and violet; 28-37 blue, green, orange and red; 38-46 blue, green, yellow and violet; 47-55 orange, red, yellow and violet; 56-64 all stars. Formerly I tossed three coins six times to get a number or numbers. In 1969 Ed Kobrin at the University of Illinois programmed the I Ching for me, so that now I refer to a printout. I have made tables relating all the numbers less than 64 to 64. When this tracing is finished . . . I translate the points in space into musical notation (the 12 tones), and then distribute these tones into the available octaves by means of chance operations.
John Cage
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