Piano Chords - Circle of 5ths Fully Explained and Application to the Piano
Easy to read and understand. I read it cover to cover in one evening. https://ringtonesnoise.com I've studied basic music theory in school and taken piano lessons from 3 different instructors and none of them explained the circle of 5ths in a manner that made any sense to me. This e-book is fantastic. It explains the purpose of the circle by breaking down and explaining the concept and structure of the circle, layer by layer. It even instructs you on how to make your own personal rotary circle. This tool is a musician's best friend, especially if you play by ear! Prior basic chord and scale knowledge is not required but it is a big help.
I like the way she makes this subject easy to understand and the illustrations are very helpful. There's a number of links to her website which I thought was good if you wanted to take further instruction in other aspects of piano playing. Glad i bought this especially since the kindle price was good and I can have it on different devices. https://soundcloud.com/maddieparrot/sets/work-out-or-get-out
This is the clearest, most elaborated, intelligent explication of the Circle (or Cycle) of Fifths I've seen, together with the author's inventive circular-slide-rule for working with it. Excellent illustrations.