Question How to loop/fade/silence background music properly (theory)

Hello,

I was looking for theory/articles how to properly loop background music to avoid annoyance. After working on one game for a while, I found that I start hating background music by myself. So I assume users do not like it after some time either =) So I believe I need to have 3-5 different one minute long tracks which could be looped.

How many times I should play each before changing one to another? Should each track be played random amount of times, may be 1-3, since average size of music is always 3-4min? How long and smooth this change should be? Is it better to make one track fade away and another fade in or should they smoothly fade from one to another? Should I have silence moments, to let user relax a bit?

I believe there is a huge theory behind that but since I am newbie, any basic tricks will be better than no tricks =) Any information, keyword to keep research in proper direction is highly appreciated.

Thanks in advance,

Andrew