Western tonal music is based off of 7 pitches within a given diatonic key. Our key system can be based on either a major or minor tonality. However, earlier in history there was a larger variety of tonalities called modes. Modal key centers and scales still impact certain types of modern day music, so it is important to have an understanding of these scales.
The idea of displacement described above can be used to derive the pitches of any of these scales. We only need to remember the number of the mode according to the order I listed above. We can then relate that to a corresponding major key signature. For example, an F Lydian scale would be an F scale with the key signature of C major because Lydian is the fourth mode and F is the fourth scale degree of C major.
There are many modern day musical applications for modes. Some styles of music utilize a modal key center instead of a major or minor one. Also, jazz improvisation relies heavily on the use of modal scales. Many chords can be associated with specific modal scales that will provide the optimal pitches to use while improvising over that chord. Finally, composers can use modes to express melodic motifs that go beyond the expressive confines of major or minor. All of these reasons bring validity to the study and practice of modal scales for any musician.
Ray Melograne received his BA and ME in music education from Queens College. He is currently teaching music in the NY public schools. He also teaches privately on the Zoen.com network.