If you want to get deeper into theory and finding keys (which isn`t always as straightforward as suggested) try looking up the Circle Of Fifths on wikipedia. Print out the Image, you can see how different chords and scales can be connected - thats only one approach, theres different ways of looking at it - plus playing differrent types of scales (as you`ve mentioned) with the same tonic will give a song many different `feels`.
__________________
No Bosses, Just Music
|