Noteworthy magic.. hmmm... hard to say on that. Many of the RL magics are only "visible" as magic to those that can detect it.
In game terms... first I'd have to be making a spellcraft check to determine if I noticed that someone was playing with energy. Perhaps I'd notice it as a blue spark around the person. Or in a really energetic musician or other artist, I might see a orange tinge to them. Failure would mean I either didn't see the activity, or that I saw it but didn't realize what I was seeing.
In game terms... first I'd have to be making a spellcraft check to determine if I noticed that someone was playing with energy. Perhaps I'd notice it as a blue spark around the person. Or in a really energetic musician or other artist, I might see a orange tinge to them. Failure would mean I either didn't see the activity, or that I saw it but didn't realize what I was seeing.