I want to write some music, maybe mix other songs as well. I want to be able to write up some melodies/harmonies, or lay down some beats and mix them to my heart's content, with different instruments (or vocals?) and so forth, but I don't want to deal with physically recording it myself. Most importantly, I have some money to spend on software, but I do not have space to put lots of hardware! I want to have the option of taking my laptop to the airport and making music on my layover if I want to. So I'll obviously need some high-quality sample libraries along with composition software and nice headphones.
My question is, what else is actually necessary? I presumably need a DAW of some kind, but I have no reference point for their quality. Do I need (or should I get anyway) a separate program for writing out compositions in real notation? Is there any way to integrate these two things, or software that does both?
I suppose this is as much a workflow question as anything else. Whatever software I end up with, I'd like my process to feel a little more organized than just haphazardly dropping samples onto tracks. I run Windows (XP and 7), for what that's worth.