THEORY OF 3JCN MUSIC NOTATION How to find major/minor chord of a song?
PLUS NOTES: for key signature [ +f, c, g, d, a, e, b ]
Start from "Fa", count up five notes: Fa Sol La Si Do, we get the second plus "Do". Repeat count up five notes again and again we will get the rest of plus notes. To know the main chords of the song: take a half-step up from the last sharp key in Key Signature to find Major chord, then go back three half-steps from Major chord, we get Minor chord.
For example: Find major chord and minor chord of a song which has the information line as follows: (beat = 100) 4/4 [+f , +c, +g]
After Fa plus must be Do plus since Fa, Sol, La, Si, Do (up five notes). After Do plus must be Sol plus since Do Re Mi Fa Sol (up five notes). Because +Sol is the last plus key in Key Signature, the next half-step will be "La" therefore "A major" is the major chord of this song. From A we go back three half-steps: +Fa <---- Sol<---- A therefore "F plus minor = +Fm" is minor chord of this song. 1 half-step + 2 half-steps = 3 half-steps (From +Fa to Sol is 1 half-step; from Sol to La is 2 half-steps)
MINUS NOTES: for key signature [ -b, e, a, d, g, c, f ]
Start from "Si", count up four notes: Si Do Re Mi, we get the second minus "Mi". Repeat the process for the rest. To find major chord, go up five notes from the last minus key For Key Signature has more than two minus keys, then the second key from the last minus key is major chord of the song. Finding the minor chord of the song is the same method with Plus (go back 3 half-steps from Major chord).
For example: Find major chord and minor chord of a song which has the information line as follows:
(Andante) 3/4 [-b, -e]
After -Si must be -Mi since Si, Do, Re, Mi. (up four) Because -Mi is the last minus key, we go up five to find the major chord: Mi, Fa, Sol, La, Si therefore "minus Si major" is the major chord of the song (or because Si minus is the second minus from the last, therefore minus Si major is the major chord). From Si, we go back two keys: Sol <--- La <----- flat Si therefore "Sol minor = Gm" is the minor chord of the song. 2 half-steps + 1 half-step = 3 half-steps (From Sol to La is 2 half-steps, from La to -Si is 1 half-step)
Advantage of Using Key Signature:
By using key signature, we do not repeat the "+" sign or "-" sign many times in a song body, so the song will be looked neater.