Can someone tell me why an A chord on the Guitar is X A E A C# E when I thought it was just A C E because of the formula 135, where does the sharp on the C come from?
A Major Scale:

``````
A B C# D E F# G#
1 2 3  4 5 6  7``````

A C E is an A minor chord. it follows the intervals 1 b3 5 when compared to the A major scale. Intervals stated in this way are always relative to the natural major scale.
Yeah, you're thinking of the A minor scale.
Quote by DominoK
Can someone tell me why an A chord on the Guitar is X A E A C# E when I thought it was just A C E because of the formula 135, where does the sharp on the C come from?

the "raw" letter names are ACE, but to derive an A Major chord from a scale using the 135 formula, you need to use the A Major scale, which means you will have to know its key signature as well.

A major Key sig = 3 sharps (F#, C#, G#)

A major scale = A B C# D E F# G#

A Major triad = A C# E

similarly you can derive an A minor triad from the A minor scale

A minor key signature = no sharps, no flats

A minor scale = A B C D E F G

A minor triad = A C E

You can also construct triads from an intervallic formula:

R + M3 + P5

example:
root = A
up a M3 = C#
up a P5 = E

or

R + M3 + m3 above last note ( the "3rd")

example:
root = A
up a M3 = C#
up a m3 = E

All 3 methods will give you the same answer. A Major triad = A C# E
Last edited by GuitarMunky at May 12, 2008,
Quote by GuitarMunky
R + M3 + M3 above last note ( the "3rd")

example:
root = A
up a M3 = C#
up another M3 = E
Some people do swear by this method, but I personally find it confusing and the least useful when forming chords. The relationship between the notes in a chord, however, is good to know.

Edit: This is not a criticism on Munky.

Edit 2: While the second method works, it requires knowledge of which intervals come from which scales and is more complex than just lowering/raising the 5, 7, 2, 3, whatever from the note in the major scale as the first method described. That first method is going to be the one used a lot.
Last edited by bangoodcharlote at May 12, 2008,
Quote by GuitarMunky

You can also construct triads from an intervallic formula:

R + M3 + M3 above last note ( the "3rd")

example:
root = A
up a M3 = C#
up another M3 = E

Would i be wrong in saying this is incorrect?

Surely it is a Maj 3rd then a Min 3rd?
If you put the A note as the number I posistion of the diatonic intervals

1 W 2 W 3H4 W 5 W 6 W 7H1

A C# E

anyway..if you look on the piano..there's not a black key between
the B and C note.

The key of C is your reference piont (all of the white keys on the piano)
1/2 step between 3/4 (note E and F) ...7/8 (note B and C)

You have to adjust the notes with # or b to keep the intervals
the same as the diatonic scale, if you start you count from a different
note then C.

The C# came from...
There's 2 full steps between I and III

There's only a 1 1/2 step between A and C
Last edited by Ordinary at May 12, 2008,
Quote by branny1982
Would i be wrong in saying this is incorrect?

Surely it is a Maj 3rd then a Min 3rd?

your correct. I didnt realize I did that.

R + M3 + m3 is correct.

thanks for catching it.

Quote by bangoodcharlote
Some people do swear by this method, but I personally find it confusing and the least useful when forming chords. The relationship between the notes in a chord, however, is good to know.

Edit: This is not a criticism on Munky.

Edit 2: While the second method works, it requires knowledge of which intervals come from which scales and is more complex than just lowering/raising the 5, 7, 2, 3, whatever from the note in the major scale as the first method described. That first method is going to be the one used a lot.

all 3 methods are fine. There is no reason to insinuate any flaw in using them. My text books explain them that way. Professors explain it that way. I used all 3 so the TS would have more options and could find the best method for their knowledge level.

anyway here is the corrected version. (sorry for the original typo, can't believe I didnt catch it)

the "raw" letter names are ACE, but to derive an A Major chord from a scale using the 135 formula, you need to use the A Major scale, which means you will have to know its key signature as well.

A major Key sig = 3 sharps (F#, C#, G#)

A major scale = A B C# D E F# G#

A Major triad = A C# E

similarly you can derive an A minor triad from the A minor scale

A minor key signature = no sharps, no flats

A minor scale = A B C D E F G

A minor triad = A C E

You can also construct triads from an intervallic formula:

R + M3 + P5

example:
root = A
up a M3 = C#
up a P5 = E

or

R + M3 + m3 above last note ( the "3rd")

example:
root = A
up a M3 = C#
up a m3 = E

All 3 methods will give you the same answer. A Major triad = A C# E

TS, I hope this makes sense and is helpful to you. Any questions, just ask.
Last edited by GuitarMunky at May 12, 2008,
Stop speaking this alien language I don't understand!