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Next: Gravitational Tapestry 2 Up: Piece Descriptions Previous: iICEsCcRrEeAaMm


The title Picking is a double entendre which captures two important components of the piece. In one sense, Picking represents the technique of plucking a stringed instrument. The only timbre used in this piece is that of the Karplus-Strong plucked-string algorithm developed at Stanford in the early 1980's.

The second facet of Picking is the meaning "to choose." Most of the compositionally controlled elements in the piece are generated by random choices created with first-order Markov transition tables. Transition probabilities control all performance aspects of the K-S algorithm including: pitch, rhythm, duration, loudness, pick position on the string, and pan location between loudspeakers.

Picking was realized in Rick Taube's CM (Common Music) LISP environment for algorithmic composition. The composition was generated with 85 calls to a single algorithm which generate notes for the piece using the following format:

   (pick time count p1 p2 p3 r1 r2 r3 r4 tempo)

where time is the starting point of the algorithm during the piece, count is the number of notes to generate, "p1 p2 p3" are three pitches to choose from, "r1 r2 r3 r4" are four rhythms to choose from and tempo is the overall speed of the algorithm. Here is the opening of the score for the piece:

;       time cnt pitches rhythms tempo
   (pick 0.5 1 'c3 'c3 'c3 1.00 1.00 1.00 1.00 2 )
   (pick 1.0 1 'd3 'd3 'd3 1.50 1.50 1.50 1.50 4 )
   (pick 1.75 1 'a3 'a3 'a3 1.00 1.00 1.00 1.00 16)
   (pick 4.0 20 'c4 'c4 'c4 0.25 0.50 0.75 1.00 4 )
   (pick 5.0 20 'd3 'd3 'd3 0.25 0.50 0.75 1.00 4 )
   (pick 6.0 20 'a4 'a4 'a4 0.25 0.50 0.75 1.00 4 )
   (pick 8.0 15 'r 'd3 'r 0.25 0.50 0.75 1.00 1 )

Note that the first three lines of the score each generate one note, and since all of the pitches and rhythms are the same, the pitch and rhythm of that note is precisely determined. The next four lines gradually overlap the pitches c4, d3 and then a4 within a range of rhythms. Each time music is generated from the score there will be a different configuration of notes due to the built-in randomness of the algorithm, but the basic musical structure is preserved due to the constraints given by the sequence of function calls to the pick algorithm.

next up previous
Next: Gravitational Tapestry 2 Up: Piece Descriptions Previous: iICEsCcRrEeAaMm

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