First released in 1995, this is a companion to the book of the same name. David Toop, author of the book and a respected musician in his own right, also 'curated' this collection of music telling the story of the diverse Twentieth Century influences that fed into the development of modern ambient music, all the way from Debussy to Aphex Twin via Miles Davis and The Velvet Underground.
When I say these CDs tell a story, I don't mean that they do so in the form of a linear narrative. One of the key strengths of this collection is the non-chronological track listing, which enables Toop to develop the themes and connections he makes in the book in more depth, and in some interesting and non-obvious ways. It's also clear that he is as interested in the nature of sound itself as in music per se; in fact, he's obviously keen (as in his own music) to break down boundaries not only between different types of music, but also between 'music' and 'non-music'. Thus, for example, you get My Bloody Valentine buzzing their way into an atmospheric piece by Brian Eno; which merges into the chanting and bell-ringing of a Buddhist ceremony; which then segues into some musique concrète featuring whistling, blaring traffic sounds; followed by a wildlife recording starring some surprisingly tuneful-sounding, if noisy, howler monkeys.
It's all rather idiosyncratic, of course, and inevitably everyone who listens to these CDs will wonder why a certain artist is / isn't represented. (No Steve Reich? Why not, given his influence on hip-hop and trance? Stockhausen is mentioned in the liner notes, but his music is conspicuous by its absence.) But by and large I think the story Toop is telling makes sense, and I'm particularly impressed with the way the tracks have been edited to flow into one another in a continuous sequence without breaks -- very much the 'ocean of sound' of the title, in fact. It's rather as if a very good DJ had decided to produce an evening's worth of ambient and experimental music instead of dance stuff.
I'd say this is as good a place as any to start if you want a historically-literate, thinking person's introduction to the avant-garde end of popular music. Better still if you get a copy of the book too and read that while you're listening.