Add a note to a file?

I'm pretty new to AA. I'm not sure whether to ask how to do this or whether it's possible. On the one hand, it's a pretty obvious feature: Who doesn't want to add notes to particular audio files sometimes? After all there's more to say about a file than can easily be written in a filename. And with .pfk files sitting there, it ought to be possible, right?

So, how do you do it? Or if there's another way that people accomplish the same thing--simply to include some explanatory text about a particular audio file--that'd work, too.

Thanks.