Chapter 1 – Basic Definitions

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1
Basic Definitions

1.1          Pitches

  • A “pitch” is any note that we hear.
  • The standard piano can play 88 pitches:  A0 to C8, where C4 = middle-C.
  • For example, the notes above middle-C are as follows:

C4 (B3), C4(D4), D4, D4(E4), E4(F4),F4(E4), F4(G4), G4, G4(A4), A4, A4(B4), B4(C5)

1.2          Pitch Classes

  • Pitch classes are used to discuss pitches independent
    of octave displacement and enharmonic spelling
    .
  • Any two pitches which sound the same on an equal tempered scale (for example, C and D) or are only different due
    to octave displacement are said to belong to the same “pitch class”.
  • For example, the following pitches all belong to Pitch Class C: B4, D4 (enharmonic equivalents),
    C0, C1, C2, C3, C4, C5, C6 (octave displacements)
  • There are only 12 pitch classes in a system where each octave has 12 chromatic notes.
  • Pitch classes can also be numbered:  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. These numbers are sometimes called “Pitch Class Representatives”.
  • For this tutorial, 0 = Pitch Class C (i.e. “fixed Do”).
  • All other pitch classes will by numbered by counting the half steps from pitch-class C.
  • Therefore, C = 0,  C = 1,  D = 2,  D = 3,  E = 4,  F = 5,  F = 6,  G = 7,  G = 8,  A = 9,  A = 10,  B = 11
  • Sometimes the letter ‘T’ (for Ten) or ‘A’ is used instead of the number 10, and ‘E’ (for Eleven) or ‘B’ instead of 11.

1.3          Pitch Class Sets

  • A “Pitch Class Set” is a list of pitch class numbers:   [0, 4, 7, 10]   (note the square brackets)
  • These are also called  “PC Sets”.
  • The PC Set for a C minor triad:  [0, 3, 7]
  • The PC Set for a G major triad:  [7, 11, 2]
  • In Pitch Class sets, octave doublings and displacements are ignored:
    • [0, 3, 7, 12]  =>  [0, 3, 7]    (see the section below on modulo math)
    • [14, 7, 11]  =>  [2, 7, 11]
    • For example, all of the following can be described with Pitch Class Set  [0, 1,4]. The only difference in these chords are octave displacements or enharmonic spellings in the pitches.

  • Oftentimes PC Set notation is shown without the commas:  [037] (here is where A=T=10 and B=E=11 comes in handy, for example: [0,4,7,10] = [047T] = [047A]   (note:  this is a C dominant 7th chord)

Copyright © 2004 by Paul Nelson, all rights reserved.

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