(musTh1) Lecture Notes: Register and Intervals

Pitch Notation – Register

We will name pitch register using middle C as C4. Going down is C3, C2, etc., and up is C5, C6, etc. The register break for numbering happens between B – C, no matter what accidentals are involved. For example, the B# above middle C is B#4, despite being the enharmonic spelling of C5.


A musical interval is described by its size (quantity and its quality. Size describes the number of diatonic steps in the interval. When combined with the interval quality, an interval of a specific number of half-steps is described.

Unisons, fourths, fifths, and octaves (1, 4, 5, and 8 ) qualities are: d – P – A (diminished – Perfect – Augmented).

Seconds, thirds, sixths, and sevenths (2, 3, 6, 7) qualities are: d – m – M – A (diminished – minor – Major – Augmented).

Each movement from left to right in quality above adds one-half-step to the interval size.

Simple intervals are one octave or less in size. Compound intervals are greater than one octave. Compound intervals can be reduced to intervals one octave or less for identification purposes.

All intervals are either consonant or dissonant. Consonant intervals are stable, and require no resolution or movement away from them in tonal situations. Dissonant intervals are unstable, and require resolution to a consonant interval.

Consonant intervals come in two types: perfect consonances and imperfect consonances. Perfect consonances include the P1, P5, and P8, but NOT the P4. Imperfect consonances include m3, M3, m6, and M6.

Dissonances include all 2nds and 7ths, the P4, and ALL augmented and diminished intervals.

To identify an interval, we generally follow these steps:

  • Count the diatonic steps to determine the size.
  • Compare interval to the diatonic (white key) interval
    • If both notes have the same accidental, then the interval is the same as the white key interval.
    • If there are different accidentals for each note, then you need to compare the interval to the white key interval and adjust the quality accordingly.

Writing intervals follows the same basic steps as identifying.

  • Write the interval size.
  • Using the white key intervals as your guide, compare the written interval to the desired/indicated interval.
  • Adjust with accidental (never change the given note).


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