Improvised Music - Essays And Interviews by Jakob Thorkild Overgaard.

From the preface:

This book is the child of my extensive personal experience
as performerof musical improvisation. I have
a large number of concerts, recordings and bands in
my baggage, and throughout my career as performer
I have reflected much on the music as such, its origins,
and its effects onperformer and listener alike.
In addi...