Nimyz wrote:I did not understand what you meant in the beginning though with "My score is in 3 sharps - A Major" though. .
I'm working from written down music - little black dots rather than internet tabs. The Key Signature on my music is 3 sharps, which means either A Major or F# minor. There is no E# in the music (leading note to F#) and my first chord is A, so I reckon I'm on fairly good ground saying it's in A.
Nimyz wrote:And also, if the scale would be A natural minor, then only the F#-chord he uses is an accidental, no?
You're in the ballpark, but do not confuse scales and chords. There is an F# in the A melodic minor scale, and there is a chord of F#m in A Major.
Nimyz wrote:... often then there are no real answers as to why some (chords in) songs sound good and others do not.
This can be down to luck, but the classic example is Hendrix's Hey Joe. the chord sequence is C, G, D, A, E.
No obvious connection? Wrong. It all proceeds in 5ths.
G is V of C
D is V of G
A is V of D
E is V of A
Keep up the theory studies. It pays dividends.