Music Theory
Acoustic Composition
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What is Harmony?

In it’s most basic occurrence, harmony is the result of two or more pitches played at the same time. Usually when thinking of harmony we think of sounds that are pleasing to the ears, however, anyone who has played two adjacent notes on the piano at the same time knows that not all harmony sounds pleasant. In music theory we use the terms Consonance and Dissonance to describe sounds that are “pleasing” or “displeasing,” however, pleasing and displeasing often depend on context while consonance and dissonance are empirical terms.

Hopefully you remember from our last lesson that an interval is the distance between two notes. While we were primarily concerned with “horizontal” or melodic intervals in the previous lesson, today we’re about to look at “vertical” or harmonic intervals. Here are all of the harmonic intervals inside of an octave, grouped into consonant and dissonant intervals:

Consonant Intervals

Let’s take a closer look at consonant intervals

  • Minor 3rd (m3): 3 half steps
  • Major 3rd (M3): 4 half steps
  • Perfect 5th (P5): 7 half steps
  • Minor 6th (m6): 8 half steps
  • Major 6th (M6): 9 half steps
  • Perfect Octave (P8): 12 half steps

Dissonant Intervals

Note: the Perfect 4th is often treated as a consonant interval in popular music

Let’s take a closer look at dissonant intervals

  • Minor 2nd (m2): 1 half step
  • Major 2nd (M2): 2 half steps
  • Perfect 4th (P4): 5 half steps
  • Augmented 4th / Diminished 5th / Tritone (A4, d5, tt): 6 half steps
  • Minor 7th (m7): 10 half steps
  • Major 7th (M7): 11 half steps

Intervals are great for ear training and for composing 2 part harmonies or polyphonic lines, however, for most musicians since 1722 harmony means chords and chord progressions.