A live, ever growing, on-line theory book where you can actually listen to the theoretical explanations given or -as you prefer- read the theoretical explanations of what is heard. For instance, say you are reading about First mode and you are looking at its apechema. Next to it, there is one (or more) sound link with example(s). Then talking about katalikseis, again, sound examples of katalikseis. Then talking about elxeis (melodic attractions), same thing. Not a primer/tutorial, the aim is to go into details with time. My initial plan is to include information about the BM modes and chroai. For the theoretical content I am going to use various sources as I see necessary. Where there are different views, I will mention them. The content will be always up for discussion/correction and, as always, enjoyment.