Guitar Theory: Roman Numerals and the Major Scale Chord Sequence How to Play C form Chord Voicings on the Guitar How to Play Pentatonic Pattern 5 on the Guitar

# How to Compare Scale Formulas and Structures on the Guitar

On the guitar a scale or chord formula is its pattern of steps and intervals. For example, a major triad is 1-3-5. A major scale is 1-2-3-4-5-6-7. The following charts compare the different scale formulas of the major scale modes that are used for keys and chord progressions.

Don’t worry about memorizing all the charts; just use them as a tool to help you better understand the relationship between the modes and their structures and the major scale.

Here is a comparison of the interval structure for the six main modes of the major scale. (Locrian mode is not included because it’s more of a theoretical mode.) Notice the relative major and relative minor here because they’re used the most and are considered to be plain, natural scales.

Roman numerals are also included so you can see how the major and minor chord sequences relate to the major scale.

Degree/Chord Mode Name Interval Structure Roman Numeral Sequence
I Ionian (plain major) 1-2-3-4-5-6-7 I-ii-iii-IV-V-vi-viif5
ii Dorian 1-2-f3-4-5-6-f7 i-ii-fIII-IV-v-vif5-fVII
iii Phrygian 1-f2-f3-4-5-f6-f7 i-fII-fIII-iv-vf5-fVI-fvii
IV Lydian 1-2-3-s4-5-6-7 I-II-iii-sivf5-V-vi-vii
V Mixolydian 1-2-3-4-5-6-f7 I-ii-iiif5-IV-v-vi-fVII
vi Aeolian (natural minor) 1-2-f3-4-5-f6-f7 i-iif5-fIII-iv-v-fVI-fVII

Here is what all these chords look like when you build out each mode in the sample scale of A major.

Mode Name Chords
A Ionian (plain major) A-Bm-Csm-D-E-Fsm-Gsmf5
B Dorian Bm-Csm-D-E-Fsm-Gsmf5-A
Cs Phrygian Csm-D-E-Fsm-Gsmf5-A-Bm
D Lydian D-E-Fsm-Gsmf5-A-Bm-Csm
E Mixolydian E-Fsm-Gsmf5-A-Bm-Csm-D
Fs Aeolian (natural minor) Fsm-Gsmf5-A-Bm-Csm-D-E

Finally, here is a chart of parallel modes. Here, the term parallel means different scales that all center on the same primary pitch. In the comparison in this table, the tonic pitch remains A for each mode. You compare A major to A Dorian to A Phrygian and so on. The parent major scale is different in each example here.

Mode Name Chords Parent Scale
A Ionian (plain major) A-Bm-Csm-D-E-Fsm-Gsmf5 1st mode of A major scale
A Dorian Am-Bm-C-D-Em-Fsmf5-G 2nd mode of G major scale
A Phrygian Am-Bf-C-Dm-Emf5-F-Gm 3rd mode of F major scale
A Lydian A-B-Csm-Dsmf5-E-Fsm-Gsm 4th mode of E major scale
A Mixolydian A-Bm-Csmf5-D-Em-Fsm-G 5th mode of D major scale
A Aeolian (natural minor) Am-Bmf5-C-Dm-Em-F-G 6th mode of C major scale

Seeing the chords of parallel modes like this gives you an idea of how many options you have when approaching a composition in the key of A. What key of A are you going to use? A major or A minor? Plain A major, Mixolydian, or Lydian? Natural A minor, Dorian, or Phrygian? Perhaps you want to try a mixture.