I've literally been composing and writing music for years. The style of music I write has a lot to do with the mood that I am in at that time. So I am not just limited to one type of music style which allows me to expand even more in creativity, etc.
I'll be perfectly honest with you...
I think life would be the answer to this question. It has a lot to do with what I am going through at the time and trust me- I dont have a problem in writing out my feelings or experiences lyrically and musically.
A variety from hardware to software and all real instruments