Hey
@MiNDSHiFT !
That's a great question! Here comes a book
Firstly, Think of a Key as an invisible musical handbook - non-physical, not specific to your Guitar but instead to all music. It's like a musical cheat sheet in your head!
To answer your question:
You can use as many chord 'shapes' as you like as long as the chord type (Major/Minor/Diminished) you're selecting falls within the Key. Remember, the physical shape you make on the Guitar is only the result of plotting out the information of each chord.
In short, a Key is just a Family of chords, built from the notes of a Major Scale. It's so easy to build a key too!
G Major Scale: G A B C D E F# -
7 notes
G Major Key: G major A minor B minor C Major D Major E Minor F# diminished -
7 chords
All I did was know all the notes in a G Major scale and follow this pattern to get all the chords in it's Key:
1.
Major 2. Minor 3. Minor 4. Major
5. Major 6. Minor 7. Diminished
****The reason the pattern turns out like this is by starting at each note of the scale and building a 3 note chord using the 'pick one, miss one' method - Select a note, miss the next, select the next, miss the next etc until you have 3 notes ****
if you do this from G you get: G B D - a G major Triad - and so on for the other chords kn the Key - for the next chord you'd do the method from A.
So to know all 12 keys, you just have to know all 12 Major scales, and follow the above pattern.
Physically on the Guitar you can learn 1 Major scale shape, 1 Major chord shape, 1 Minor chord shape and 1 diminished chord shape and play the chords/solo in any key you want! You would just move the scale shape/chords around in accordance to which key you're in
Pentatonic wise - the pentatonic scale is just a pattern of 5 notes, cherry picked from your Major Scale, so it still relates directly to the Key.
I know that's a lot to unpack, so try and digest it slowly. It will make sense as soon as you hear it on your instrument