Is There a Way to Write Things Down Quickly?

i often find myself in situations where there's just something that i want to write down quickly, and i'm not even sure exactly what it is or where it's going to go. I feel like i'm half way between two music systems, and everything is just a mess everywhere. My music system is kind of a mess because i have a bunch of music that i bought through i tunes a while back. And ideally i would like to compress those two icons down to one icon in the future. But no, this is where we are at the moment.