Notes:

• The word "Authentic" is used here in contrast to the so-called "Plagal" Modes. The Plagal Modes, however, are simply derivatives of the Authentic ones.
  
  
• Each vertical line represents a note in the Mode and the distance between lines, therefore, represents the size of the melodic step (known as interval).
  
  
• The larger melodic intervals are known as tones, and the smaller intervals as semitones.
  
  
• The Locrian Mode was rejected as impure because it contained no dominant.  A dominant is defined as being a perfect fifth (seven semitones) above the first note (known as either the final or tonic) of the mode.  It was considered important because of its strongly consonant relationship to the tonic.  The perfect fifth is second only to the octave in ts degree of consonance.  For a comparison of these and a more detailed discussion of ideas of consonance and dissonance see Medieval ideas of consonance and dissonance in Week 2.
  
  
• Note that semitones are always separated by either two or three tones in the Church Modes. Other distributions of tones and semitones are, of course, possible, but were not sanctioned by the Church.
  
  
• The medieval music theorists came up with mathematically precise definitions of the tone and the semitone. It is obvious, however, that differences in tuning of these intervals would affect very noticeably the characteristic sound of a mode. The precise tuning of the scale steps within the octave was to become a long running controversy in J. S. Bach's lifetime. For an opportunity to listen to different tunings (e.g. mean tone and equal temperament) see under Temperament on the Links page.
  
  
  

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