Scales are a guide to be familiar with the notes. Best theory I got when I came back to guitar after 17 years of not touching one was at the Grey Fox Bluegrass Festival at the Slow Jam the guitar guy showed a chart emphasizing the 1, 4 and 5 of the scale as most important notes
1 4 5 6m
I ii iii IV V vi vii dim
C D E F G Am B key of C major
G A B C D E F# key of G major etc.
So most played chords in any major key are the I, IV, and V. The vi or minor 6 is the next most important and any other of the notes would be minor except for the 7th note which is diminished. Knowing this helps you to jam along at bluegrass jams when you don't know the songs...mostly simple songs....and this helped me start to write my on songs...I took off with it. Another good thing to know is the key of C major and the key of A minor are related in that they share the same notes and same chords. I have a mandolin chord book that groups all the chords by key putting the major key with it's minor 6th.
Using this numbering system above is how you transpose to another key. Write out the other key and assign the number to it....see above....Well you have to look at the circle of fifths to know how the sharps and flats are added and I keep a copy of that on my wall.
Years ago I took guitar lessons and the first teacher made me read music so I learned to read notes but then I fired him and got another teacher to teach me to play by ear. But that first year helped me really understand timing and helped me read tab. Some theory is very useful...to know what you are playing
Other good things to know is the notes on the fat E string and notes on Fat A string so you know what key you are in for 5th root and 6th root scales...also to know what bar chord you are playing.
Another easy tip is to understand the octaves...so at the 5th fret bass string is A, skip one string and 2 frets down is an octave and that is also an A so it helps you to know what those notes are...helps when you want to resolve to the root note when playing in box 1 as well as there are some root 4 bar chords as well.
I think it's important to have fun with guitar and not be burdened with too much theory. Many have quit because of Berklee style teachers making them read every note on the guitar neck which is laborious...but as you can see it's helpful to know many of those notes. Everyone has to find what works for them. I find if I am playing from tablature I end up analyzing it to see what scales I am playing out of and why does this or that work. Some theory is very useful especially the theory that relates to the guitar neck. Once you know notes on 5th and 6th string you know 1st string too.
Now I am finally taking the time to learn other chords, some 9ths etc. and triads and many things I learned in the past that I haven't gone back to yet, and working on lead guitar again. I am very happy for the internet and I love Rob's lessons!
Another useful thing is seeing how the minor pentatonic scale pattern fit together on the guitar neck...again they are only a guide and one has to use those notes creatively to make good music...I am struggling with that now. Ugh. I learned the major scale years ago but use the pentatonic much more often. For awhile I strummed and sang and now I am going to push myself to be a better guitarist. Cheers!
