In all actuality you don't even need an instrument to learn music theory, I learned what I know on guitar. I'm self taught, and it is true that you can apply what you know to any instrument.

I can play chords, and some melody on keys, and I do play several other stringed instuments.

I could figure out scales, and scale patterns on keys, if I wanted to put my guitar down long enough. I'm mostly an ear player so to speak, but I can sight read music also. Since I'm not as fast at it, I rely mostly on my ear, and the theory I do know.

I like the guitar better because you can play scales with open strings, or you can play them in other postions. Btw the major scales generally cover two octaves. In other words if you play a C major scale starting in the 8th fret on the 6th string, you have covered two octaves by the time you get to the last note in the 8th fret on the 1st string. If you want to go the 3rd octave, whole step is the distance of two frets, and half step is the distance of one fret.

From the C note in the 8th fret on the 1st string, go a whole step to the D note, a whole step to the E note, half step to the F, whole step to the G, whole step to the A, whole step to the B, and a half step to the C note in the 20th fret on the 1st string.

W W H W W W H, is the major scale pattern.

Learn the notes on the fretboard, which is actually much simpler than you think. You'll be playing scales in no time, the major scale is the same pattern no matter where you play it. The pattern only varies if you're using open strings to play the scales.

I don't think you need to learn on a keyboard to learn theory, and grasp the concept. As I said earlier you can apply it to any instrument, and even Sunfly will agree after learning to apply it to guitar.

You can play a major scale using only one string, but the majority of the time they are played using all the strings in succession.

This lesson has no video, and the scale is actually reversed, but it will show you the position for the A major scale. http://www.guitartricks.com/lesson.php?input=7822

This lesson is the same scale, but using open strings. http://www.guitartricks.com/lesson.php?input=7922

I hope this will help you figure out what you want to know, and then you'll realize how simple it is.

JD