Quick Tip: "I D P L M A" Key Signature Guide
Are you tired of using either major or minor scales in your compositions? Have you ever heard of modes or modal scales? For those who want to bring something interesting to their compositions, try using the notes from one of the modes and you will immediately hear the difference. For more information about what modes are or how to use them, visit Ryan Leach's premium tutorial "An Introduction to Modes".
In this quick tip I want to give you a little guide on how to figure out the right key signature for the specific mode. The only thing you have to remember is this row "I D P L M A", which refers to 6 most used modes: I - Ionian, D - Dorian, P - Phrygian, L - Lydian, M - Mixolydian, A - Aeolian. I purposely skipped the last one - Locrian mode because it is considered more of a theoretical mode and it is hardly ever used.
Whether you are preparing yourself for a music theory exam, or you are about to compose a piece using one of the modes and you are not sure what key signature or notes you should use, this quick guide may help you.
In our example we're going to look at the key of G and its different key signatures when it comes to the particular modes.
I - Ionian mode
Let's start with a G Ionian mode. This mode is the same as today's major scale, so G Ionian mode uses the same key signature as G Major (1 sharp) and the notes are: G, A, B, C, D, E, F#, G.
G Ionian mode:
D - Dorian mode
Now let's say you want to compose a piece in a G Dorian mode. Take a look at the "I D P L M A" row. Letter "D" is the second in a row, which means you have to use the same key signature as F Major (1 flat), because F is a major second below G, so the G Dorian mode uses these notes: G, A, Bb, C, D, E, F, G.
G Dorian mode:
P - Phrygian mode
If you want to use the G Phrygian mode, you have to use the same key signature as Eb Major (3 flats), because Eb is a major third below G, so is the letter "P" third in our row (I D P L M A). G Phrygian mode uses these notes: G, Ab, Bb, C, D, Eb, F, G.
G Phrygian mode:
L - Lydian mode
The rest of the modes work in the same manner. G Lydian mode uses the same key signature as D Major (2 sharps), because D is a perfect fourth below G, so is the letter "L" fourth in our row . G Lydian mode uses these notes : G, A, B, C#, D, E, F#, G.
G Lydian mode:
M - Mixolydian mode
G Mixolydian mode uses the same key signature as C Major (0 flats/sharps), because C is a perfect fifth below G, so is the letter "M" fifth in our row. G Mixolydian mode uses these notes: G, A, B, C, D, E, F, G.
G Mixolydian mode:
A - Aeolian mode
The sixth in our row is the letter "A", so if you want to use a G Aeolian mode, you have to use the same key signature as Bb Major (2 flats), because Bb is a major sixth below G. G Aeolian mode uses these notes: G, A, Bb, C, D, Eb, F, G.
G Aeolian mode:
You can use the same method for every single key.