Or simply when compared to the major scale (Ionian mode),
Originally Posted by prscat33511
Starting on the 2nd scale degree and playing to the 2nd scale degree one octave up or down is Dorian mode.
Starting on the 3rd scale degree and playing to the 3rd scale degree one octave up or down is Phrygian mode.
Starting on the 4th scale degree and playing to the 4th scale degree one octave up or down is Lydian mode.
Starting on the 5th scale degree and playing to the 5th scale degree one octave up or down is Mixolydian mode.
Starting on the 6th scale degree and playing to the 6th scale degree one octave up or down is Aeolian mode.
Starting on the 7th scale degree and playing to the 7th scale degree one octave up or down is Locrian mode.
For example, if we want to discover the name of the major scale in which B Lydian appears, all we need to do is look for the scale in which B is the fourth note. We know that the scale is going to be an F scale because the fourth note letter when counting from F is B ( F, G, A, B). We also know that the fourth note in the major scale is a perfect 4th, which is five half steps up from the root. The note five half steps (frets on a guitar) down from B is F#; therefore, B Lydian appears in the key of F# major.
If we want to find the notes in B Lydian without having to look them up (or God forbid, memorize them, which is not going to happen at my age), all we need to do is to remember the interval spacing pattern for the major scale (Ionian mode) and know how to rotate the pattern to make the scale degree (note number) of the mode the root note of the pattern. For example, as mentioned above, the interval spacing between notes in the major scale follows the pattern WWHWWWH, where the letter W denotes a whole step between notes and the the letter H denotes a half step between notes (one needs to commit this pattern to memory). The first W in the pattern is the distance from the root note to the 2nd note in the scale; therefore, in order to rotate the pattern such that the 2nd note is now the root note, we remove the first W from the beginning of the pattern and append it to the end of the pattern. Effectively, we remove the note number minus one characters from the beginning of the pattern and append them to the end of the pattern (circular shift n - 1 characters).
However, there is a problem with this scale as it stands. All scale degrees have to have a unique letter; therefore, we have to resort to an using enharmonic equivalent name for one of the F notes. Enharmonic equivalent note names are different names for the same note. The note letter missing in the scale is E; therefore, we need an E note in the scale. The enharmonic equivalent note name for F is E#; therefore, B Lydian is B, C#, D#, E#, F#, G#, and A#.
Deriving the pattern for Lyndian mode from the pattern for the major scale (Ionian mode)
Step 1.) The pattern for the major scale is WWHWWWH.
Step 2.) Lyndian mode is the 4th scale degree (note number) in the major scale; therefore, we remove 4 - 1 = 3 letters from the beginning of the pattern, leaving WWWH.
Step 3.) We append the characters that we removed in step 2 (WWH) to the end of the remaining pattern (WWWH) from step 2, yielding the pattern WWWHWWH.
The interval pattern for Lydian mode is WWWHWWH.
Applying the pattern for Lydian mode to B Chromatic yields B Lydian.
B, C, C#, D, D#, E, F, F#, G, G#, A, A#, B
W W W H W W H
The notes in B Lydian are B, C#, D#, F, F#, G#, and A#.
If we look at the key signature for F# major, we discover that there are six sharps on the treble staff (none of which fall on the B line), which means that we have identified the correct notes in B Lydian because B is the 4th note in the key of F#.