6/22/15, 8:34 AMA Brief Introduction to Pitch-Class Set Analysis - 7

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Note: Normal form, prime form, and packingNote: This page has opened in a new window. Close this window to return to your previous place in the pc-set guide.

Guides to pc set analysis, including this one, usually say that the normal forms of sets are "packedto the left." Though a convenient expression, it is not quite true. When we learned the steps fordetermining normal form (see page 4 of this guide), we learned that when two or more set formsare tied for overall size, we seek the smallest interval from first pc to second-last, then from first tothird-last, and so on, working in from the end until the tie is broken. In fact, then, we are not reallylooking for the form most packed to the left, but for the one most packed from the right!

This "packed from the right" convention is the one found in several guides to pc set analysis,including John Rahn's Basic Atonal Theory and Joseph N. Straus's Introduction to Post-TonalTheory. Allen Forte's The Structure of Atonal Music, however, favours a true "packed from the left"approach: in the case of overall ties, one looks for the smallest interval between first and secondpc, then first and third, and so on, working out to the end.

The conflict is usually discounted as a minor one, since the two approaches mostly produce thesame results. For some sets, however, the results differ. Morever, 6 out of the 208 prime forms areaffected by these differences. Below is a list of the set classes in question, with their prime formscited "packed from the right" and "packed to the left."

Forte name:

Prime formpacked from the right

Prime formpacked to the left

5-20 (01568) (01378)

6-Z29 (023679) (013689)

6-31 (014579) (013589)

7-z18 (0145679) (0234589)

7-20 (0125679) (0124789)

8-26 (0134578T) (0124579T)

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