The Orb is one of my favorite "groups" ever. In quotes, because the line-up is ever changing, with only Alex Patterson as the fixture. They are NOT trance or techno, but properly called Ambient Dub. Why? They ushered in a fusion of ambient music (as tha name suggests, an atmospheric, often beatless musix that has been coined (by Eno) as "Sonic wallpaper") with Dub Music (a bass-heavy music originating from the instrumental b-sides of reggae music). Their music wanders all over the place though, with Orbvs Terrarvm being their most impressive work - this is neo-classical music people! 
All their albums are good, except for their last, which is pretty much a signal that all good things do come to an end, even the fantastic voyage of Dr. Alex Patterson and his crew.