Originally Posted by: txladykatThanks! I actually understood the concept behind creating major chords from the scale (1, 3 and 5). The dominant 7th my teacher gave me were different. I did notice that E7 and A7 has two different ways of being played. Of course, the one you reference above is easy and I can do that with no problem. The ones I have a hard time with are the ones that require 4 fingers. My teacher taught me E7 as the Emaj with the pinky playing the added D at the third fret. I am going to check out the lessons posted below.

But why is that my teacher is teaching me to play dominant 7th with G#, E, B and D as opposed to the two options you listed above?

The D is included in the tab, it's where I wrote "open" @ the forth string up, which is the D string. Just play that string without a finger on it and you have your D note. The D note is required, that's what makes the E-Major chord a E7 chord.
An A7 would use the same formula we used to figure out E7, only this time we need to use the A Major scale: A-B-C#-D-E-F#-G#. The seventh note is G#, but remember, you have to flatten the 7th note back 1/2 step (one fret) because the chord is A7. So take G# down 1/2 step and you have G.
If the chord said Amaj7 (A Major 7) you would not flatten the 7th. You would use G# with an A Major chord because it states Amaj7. Make sense?
All you need to do for an A7 is
e|---|------|open (This is the fifth)
b|---|--C#-| ring (or pinky) finger 2nd fret (This is the third)
g|---|------|open (this is the dominant 7th note)
d|---|--E---|index (or Middle) finger 2nd fret (This is the fifth)
a|---|------|open (This is the root note "A")
E|---|------|open (Optional) or don't play low E string (it is the fifth so it works).