The Blues Scale For Guitar by Andrew D. Gordon is an invaluable guide to the blues scale, explaining how it is used to improvise in many styles of contemporary music.
Both the Blues scale and relative minor Blues scale are explained in detail, and how they are used either separately or together in the patterns for each style (the relative minor Blues scale is generally not used in minor keys) is discussed. Each of the 20 grooves in this book contains over 150 patterns in total, using notes solely from the blues scale. Each of the 20 grooves utilizes a chord progression that is commonly used for that style of music. The patterns generally start off fairly simply and become more complex as the groove progresses.
The audio files contain recordings of all the blues patterns that are notated in the book, recorded along with a rhythm section of Piano, Organ, Guitar, Bass and Drums and, on certain grooves, Percussion. Also included are extended 2-3 minute play-a-long MP3 files of all 20 grooves, enabling you to practice playing the blues patterns or creating your own for an extended period of time. MIDI files are also available.
Watch an introduction to The Blues Scale For Guitar: