IBD contains explanations, demonstrations, and examples, but most importantly, it contains a progression of interactive drills and play-along multimedia exercises that gradually develop a musician's improvisation ability.
With IBD one learns practically how to use scales and chord notes when improvising on all kinds of chord progressions.
The training strategy has two main objectives: The first objective is to train the musician in mastering the use of pure chord notes ('pillar notes' in IBD terminology) when improvising on chords, and develop a strong sense of harmonic and melodic direction. The second objective is to train the musician in mastering the use of scales and modes. The importance of mastering both chord notes and scales is explained and thoroughly demonstrated from the very beginning of the course.
IBD is mainly designed for intermediate and advanced musicians. Beginners are advised to develop some basic musical skills (chords, scales, basic technique) before starting the IBD course.
Improvisation By Degrees is not linked to a particular musical genre. While jazz musicians are the most obvious category who can benefit from the course, anybody who solos and improvises on any kind of chords -- e.g. blues, rock, bluegrass, metal, and many, many other musical forms -- will find highly effective exercises and training strategies that they can apply immediately to their own playing.