The circle of fifths is just a list of all of the fifth intervals in the musical scale. It is a circle simply because after going through the entire list, you arrive again at the note on which you started. It is also useful in that when interpreted as keys, when listed in order, each key has one more sharp or one less flat than the previous key. (Image taken from http://www.torvund.net/guitar/Theory/23-Circle_of_fifth.asp)

What is the circle of fifths? An illustration that shows the relationship of notes (and key signatures) organized in a circle of 12 locations. Each of the 12 locations has a note (or key). Each of the 12 locations has a note that is an interval of a fifth from the two neighboring locations (left and right). Mastering the understanding of the Circle Of Fifths gives the student a clear understanding of how a dominate key adds a sharp to the key signature. Like wise, adding a flat to a flat key signature provides the subdominate key signature. The circle provides 12 sharp keys and 12 flat keys. What is it used for? The uses are numerous, but is mostly an aid for a musician to organize his/her understanding of the major and minor key signatures and how these key signatures (or tonal centers) interact within musical compostions. This is exemplified by the relationships of tonality, including the understanding of Dominate and Subdominate keys, as well as, relative major and relative minor keys. How can I best take advantage of it? In addition to drawing the circle of fifths on paper in a very timely manner, the music student must be able to locate and verbilize the constant appearance of the circle of fifths within musical compositions. This includes obvious and hidden changes in tonalality, harmonic progressions, and melodic interval relationships.

If you memorize the circle of fifth, you can figure out quickly which is the dominant cord and which is the subdominant cord of the tonic cord that you might be looking at. F C G D A E B F# C# Ab Eb Bb If you are looking at E above than you know that A is the subdominant and B is the dominant.

The Circle of Fifths is a chart used to teach key signatures easily. It is set up like a clock. 1. At the top you will find C which means, the key of C with no sharps or flats. 2. Go counterclock wise to the next keys and you will find these keys(a fifth interval apart) with their key signatures a. Key of G with one sharp. b. Key of D, two sharps. c. Key of A, three sharps. d. Key of E, four sharps. e. Key of B, five sharps. f. Key of F3, six sharps. 3.For the keys with flats, start with C again and go counterclock wish, and you will find these keys(a fourth interval apart) with their key signatures: a. Key of C has no sharps or flats so it belongs to both. b. Key of F, one flat c. Key of Bb, two flats d. Key of Eb, three flats e. Key of Ab, four flats f. Key of Db, five flats g. Key of Gb, six flats