Some (Guitar) Music Theory Review

Western music is based on the major scale. To play the major scale, you need to start at some note and then do the following sequence: WWHWWWH. Each H represents half, which means you increase the frequency by one semitone, (i.e. 2 ^ (1/12), i.e. 1 fret on the guitar.) The W represents two semitones. When you start on a note1 , you can stay in the key of that note by following any rotation of the major scale sequence. The index of the major scale that you start with determines the mode you are in.2

Switching modes throughout a piece is not advised. It swaps the mood of the piece, and gives the sense you are changing your style mid performance. However, switching keys while staying in the same mode can add lots of variety to the music.

Plato suggests only playing in the Dorian and Phrygian.

  1. the root []
  2. WWHWWWH Ionian (C D E F G A B C)
    WHWWWHW Dorian (D E F G A B C D)
    HWWWHWW Phrygian (E F G A B C D E)
    WWWHWWH Lydian (F G A B C D E F)
    WWHWWHW Mixolydian (G A B C D E F G)
    WHWWHWW Aeolian (A B C D E F G A)
    HWWHWWW Locrian (B C D E F G A B)

    The notes listed to the right of the mode are the note sequences for that mode that have no flats or sharps. But a mode can start with any note.
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