I have looked for an explanation of this - that I understand, all of over the internet but I seem to come up short every time. In my jazz band, I play lead alto , and get parts that call for an improv solo. I usually do pretty well using Blues scales, but I want to know what I'm actually doing. I don't understand what the chord changes such as Dmi9, C9, B9, Dmi7, and G7 mean. I know these are certain scales that I'm supposed to pick notes from and base my solo off of, and I know what roots, 3rds, and 5ths (etc.) are but I still don't understand. My band director tells me not to worry too much, but I'm not going to be satisfied until I learn. I was hoping that maybe someone could explain this to me? I've heard it's complicated. I also, have one question: If I were to play in C9, would I start on C, or A? That's all I have. Please Help!