Digging out this thread since I just acquired and listened to the "Howard 31" comp on Artware. Despite the dull name and artwork, it's a perfect example of Mikko's description of comps that have little in common from track to track, but work so well as a unified statement. Or maybe it works because it's just an overall look at what was happening in 1994. Either way, it's full of exciting tracks (Small Cruel Party percussive rumbling; Nicolas Collins' alien 'backward guitar' and strange monologue; Klangkrieg's overly jumping mid '90s digital smear; Roger Doyle's HYSTERICALLY overly jump digital jumbles; with a decent C.C.C.C. blast track to clear the palette before ending on a docile environmental piece by Syllyk. Like I say, terrible artwork, baffling name, but really strange and great, and can still be had for under 5 euros pretty easily.
I fell out from comps for a long time because I never felt like listening to something while having to have the liner notes at hand all the time to figure out who was who. But I've gotten over that and really enjoying these strange time capsules of style or time or place.
One compilation strategy that I like more than anything is the LP-length comp with only two acts per side. I'm straining to think of too many records in this style, but two in particular are some of my favorite compilations: Höga Nord, on Segerhuva, and Er Ist Tief und Dein Wasser Ist Dunkler on Quiet Artworks. Höga Nord has already been mentioned, and deserves all the praise it gets. Each track is long enough to absorb you, distinct enough to be a contrast from the other three, and representative of a certain style that was happening at the time, like Bocksholm's metal hammering and queasy atmosphere or Vårtgård's corroded rusty blasts or Dusa's tape-damaged violin and episodic editing sequence.
Even more so, I just love Er Ist Tief, because not only does it consist of four great and distinct tracks, but even the two sides are a contrast! Side one has some VERY rusty creaking and aching from PFN (not a band that gets a lot of discussion any more) and Yeast Culture's water droplets, deployed by creating some sort of strange metal device with lots of precisely-spaced holes in it (I think). Side one is all rust and decay, while side two glows with warm electronic light, as both the Arcane Device (great track) C-Schultz pieces are purely electronic. Earth and air, cold and warm, rust and solder.
I'm hard pressed to think of too many more comps with this "four cornerstones" approach, though the Shiroseasons CD comp does come to mind. Four artists (Aube, Small Cruel Party, Daniel Menche, Kiyoshi Mizutani) each representing for a different season. I don't remember it well, so it might be time to re-evaluate. The tracks are a bit longer, too, so it would probably be more like a 2LP if released that way.