For Toop, "ambient" refers to the interpenetration of (intentionally composed) music and the surrounding background. Ambient music in the Brian Eno sense is composed music intended to supplement or "tint" the environment; other musicians incorporate natural sounds and non-traditional instruments; yet others shift the listener's attention to the listening context, like Cage's 4'33". "This blurring of the edges between music and environmental sounds may eventually prove to be the most striking feature of all twentieth-century music" (R. Murray Schafer, The Tuning of the World).
Toop extends his premise beyond its breaking point by interpreting other notable aspects of twentieth-century music as examples of the same tendency; for example the post-modern blurring of genres, boundless trance-like compositions, and electronic music in general. All of these innovations serve the contradictory impulses of listening to the entire soundscape as music and helping music lift free from its earthbound context. Twentieth-century music shifts the focus from the intentions of the genius musician to the active participation of the listener.
Ultimately Toop did not provide me with a new way of listening or introduce me to new artists I am compelled to check out.