While all Eno collaborations are amazing and have added and enriched the lives of all who made it and listen to it, for me, Eno's lps with Robert Fripp, and those with Cluster, are the most amazing that he made.
"Evening Star," Eno's 2nd and final (alas) lp made with Fripp, foreshadow Eno's ambient works to come, as it appears that Fripp was second fiddle on these reocrdings, adding his sinewy guitar as needed, and doing little else. Age and wisdom, of course, tell us that Fripp was much more involved than that, despite his sparse playing of his guitar.
Whatever the case, "An Index of Metals" is quite possibly the most astounding piece of music in all of Eno's amazingly desperse canon, foreshadowing not only his pure ambient pieces, but the forthcoming industrial movement, as well, with his tape loops and prepared use of Fripp's guitar. An astounding number, to be sure- bleak, sparse, yet emotional and full of life.
This lp has it all for fans of early textured ambient works, and is a must own.