| Improvisation: Its Nature and Practice in Music is a tremendously fascinating and informative book by the great free-improvising guitarist Derek Bailey. It discusses the role of improvisation in many musical forms, both historically and in present-day practice. One might expect a book by Bailey to concentrate on the sort of "non-idiomatic" improvisation that he plays and promotes (and, indeed, he does devote one of the seven sections of the book to that method of improvisation), but there are interesting sections on the role of improvisation in Indian, Flamenco,Baroque, Jazz, and Rock music as well. Bailey also devotes a section to improvisation and the composer.
Each section of the book is filled with interviews of leading practitioners of the style of improvisation under consideration. Some of those interviewed include: John Zorn, Jerry Garcia, Steve Howe, Steve Lacy, Earle Brown, Max Roach, and Evan Parker.
Improvisation was originally published in 1980 (by Incus records, the record label Bailey started with fellow improvisers Tony Oxley and Evan Parker) and was subsequently revised and updated in 1992. My copy of the book is the American edition, published by Da Capo Press in 1993. | 
