Principal Chords: YOU HAVE NEED IT MUST TO SING A SONG| Guitarethics.com

If you don’t know that, which chords is used on a song but if you know that which scale is used on this song, so you can play this song in that case.

If you want to play a song on C major scale. So that you can play just C major, F major and G seventh chords.
That means, major chord of root/1st note, major chord of 4th note and seventh chord of 5th note on C major scale.
C major scale: 1      2      3      4      5      6      7      8
———————C     D      E     F     G      A      B     C

CHART OF PRINCIPAL CHORDS WITH RELATIVE MINOR CHORDS
What is Relative minor ? : Relative minor is sixth note of any major scale.
That is, relative minor of C major scale is A minor scale, relative minor of G major scale is E minor scale.

I have already uploaded The 15 major scale and 15 minor scale on this website.

**********************Major********************Relative Minor**************
C =   C F G7————-[1]———Am = Am Dm E7—-[2]
G =     G C D7———–[3]———Em =    Em Am B7———-[4]
D =     D G A7———–[3]———Bm =    Bm Em F#7———[4]
A =      A D E7———–[3]———F#m =   F#m Bm C#7——[4]
E =      E A B7———–[3]———C#m =   C#m F#m G#7—-[4]
B =      B E F#7———-[3]———G#M =   G#m C#m D#7—-[4]
F# =    F# B C#7——–[3]———D#m =   D#m G#m A#7—-[4]
C# =   C# F# G#7——[3]———A#m =    A#M D#m E#7—-[4]
F =     F Bb C7———-[5]———Dm =     Dm Gm A7——–[6]
Bb =   Bb Eb C7——–[5]———Gm =     Gm Cm D7——–[6]
Eb =   Eb Ab B7——–[5]———Cm =     Cm Fm G7———[6]
Ab =   Ab Db Eb7——-[5]———Fm =     Fm Bbm C7——-[6]
Db =   Db Gb Ab7——[5]———Bbm =    Bbm Ebm F7—–[6]
Gb =   Gb Cb Db7——[5]———Ebm =   Ebm Abm Bb7—-[6]
Cb =   Cb Fb Gb7——–[5]———Abm = Abm Dbm Eb7—-[6]

[1] = On natural major scale
[2] = On natural minor scale
[3] = On sharp table of major sscale
[4] = On sharp table of minor scale
[5] = On flat table of major scale
[6] = On flat table of minor scale

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