We now broach the concept of moving the degrees within a scale. Any note in a scale may be designated as scale degree number one. The Pentatonic Scale has five notes and therefore five different modes. It is the way a scale is used that determines its mode. Major and minor scales can be viewed as modes of the same diatonic scale.
Any scale may be considered a mode but most commonly modes refer to the medieval church modes. A study of modes reveals how to establish a tonal center. Traditionally a tonal center is the result of a relationship between two notes in a scale. Most commonly the interval between these notes is a perfect fifth. Modal melodies will emphasize one of these notes and yet finish on the other. We most commonly refer to these two notes as dominant (the note that dominates the melody) and tonic (the note at rest). The Phrygian mode is the only church mode with an interval of a sixth between its dominant and tonic. None of the church modes used B as a dominant or tonic because of its imperfect relationship to F. Such taboos no longer apply and there are far more unnamed modes than named ones.

The Dorian Mode is usually described as the notes of the C-Major scale with D (the 2nd degree) as the finalis (tonic) and A as the tenor (dominant). Here we have the key signature for D-Major. The Dorian mode then starts on the 2nd degree of that scale, E, and the tenor is B.

The theoretical difference between a key and a mode is that in keys accidentals may be used and the music has harmonic (vertical) construction whereas in modes the notes are not altered and the basic construction of the music is melodic (horizontal). This is not to say that key signatures are not used in modal music. Modes move in relation to the key (see left).
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