Well like anything else, the construction of a melody. The way that it resolves naturally from one note to the other. And of courses you know you have a lot of practice in that all of the great people that came before you that wrote melodies. There's so many great melodies that started I don't know how long ago, a thousand years ago even maybe. But to have a melody that a person can listen to. I thought about that recently -- a melody that a person can listen to that they never heard before but they still can appreciate it and enjoy it. The beauty of it. Of course you can always enjoy a melody that you know, if it's something that you like. But to be able to play a melody or to write a melody or compose a melody that people can listen to and say yeah I like that, although I haven't heard it before. I think that's one of the things that -- the standards that I try to look for in playing or writing a melody.