(Haha, yeah, I did do that shrieking thing with Rye & Coke. I don't imagine that was the best idea but when I went to change it I just didn't have the heart. So yeah, it'll do that! lmao.)
I use FL Studio 4.1 (www.flstudio.com) for everything along with a slew of VST plugins and whatnot. Most of the instruments you hear come from professional quality soundfonts. As for the composition, I usually start by exploring themes or melodies and try and accompany whatever it is I come up with with a rythm of some kind. Some cases are different than others. Like in Rock Lake for example, the piano was written long before any of the strings or rythm were incorporated.