I'm having some trouble understanding the theory behind it.

Any help?
Well a major seventh is just the 7th note of its associated major scale. So if its C major, then that note would be B. In terms of Chords you usually replace the repeated root with that 7th.
A major 7th is an interval (a half-step below an octave). For example, if C is our reference point, the B above that would be a major 7th. Rephrased in terms of the fretboard, it would be the distance between this (x3xxxx) and this (xxx4xx).

A major scale inherently includes a major 7th as its 7th degree, it's not something you "add to a scale".

A major 7th *chord* is constructed as a major triad with that interval added to it. So if a C major triad, for example, is constructed by the notes C, E, and G, we would make it a major7th by adding a B to it, giving us C, E, G, and B. To translate to the fretboard with a basic example again, it would be the difference between this (x320xx) and this (x3200x).
Last edited by Brainpolice2 at Dec 4, 2011,
key of C
C scale C D E F G A B

the basic major chord is the 1 3 5 tones of the scale C E G

to make it a Major 7 you add the B - C E G B that is C MA7
You add a major 7th by taking the root note of the chord and going 11 semitones up from it (octave minus one semitone). For example, if you have a C major chord (C E G), the major 7th would be B, and Cmaj7 would be C E G B.

I recommend reading through these, it should clear up a lot for you: http://www.ultimate-guitar.com/columns/the_guide_to/the_ultimate_guide_to_guitar_chapter_i__1_introduction_-_the_guitar.html

EDIT: Wow, got beaten 3 times to it
E:-6
B:-0
G:-5
D:-6
A:-0
E:-3
Last edited by Flibo at Dec 4, 2011,
Quote by Brainpolice2
A major 7th is an interval (a half-step below an octave). For example, if C is our reference point, the B above that would be a major 7th. Rephrased in terms of the fretboard, it would be the distance between this (x3xxxx) and this (xxx4xx).

A major scale inherently includes a major 7th as its 7th degree, it's not something you "add to a scale".

A major 7th *chord* is constructed as a major triad with that interval added to it. So if a C major triad, for example, is constructed by the notes C, E, and G, we would make it a major7th by adding a B to it, giving us C, E, G, and B. To translate to the fretboard with a basic example again, it would be the difference between this (x320xx) and this (x3200x).

Thanks
Quote by Dillonski
I'm having some trouble understanding the theory behind it.

Any help?

All theory, is related to the Major Scale. If you understand the notes and intervals of a major scale, then you need to know triads and chord formulas. Learn Diatonic Harmony at least to 4 part (I teach to 7 parts). That's where 7ths come into play, and there are all kinds depending upon the chord that's built from a particular degree in a Major scale.

Quick instant gratification use, with no study/understanding needed?

OK, use it on the I and IV chords in a given Major key.

Best,

Sean