In the month or so until my band get back together I've been working on writing some new material, and want to try and expand how complex my songs are. I apologise if there are alot of questions - I'll gladly split them up if needs be.
Say I've got a nice little riff/idea in D minor. I'm happy that the relative major of that is F major, how modes fit into a major/natural minor scale, the tonality of the various degrees of the scale, and the concept of the circle of fifths. I also appreciate that a song need not necessarily change key to have a very different sound.
I'm looking at complete changes of key to try and bring a new direction to a song outside of these ideas. So ultimately, can someone explain:
a) What keys can I change to from a given key?
b) What is the theory behind the potential key change?
c) The word modulation seems to by used alot in similar circumstances. What is the difference between a key change and a modulation?
The more detail the better, as I want to understand the theory behind what I'm doing for myself rather than just follow rules blindly.