The criterion for inclusion and song order is listenability. Chronological order and tidy classification takes a backseat to how the cd sounds. Artifacts is a mixture of Rush Rarities AND their guest appearances. By Rush rarities I mean songs NOT found on any of their regular releases (not minor prerelease versions). I found that just listening to the guest appearances DOES get a little stale but mixing in the rarities keeps it exciting. And yet they all still fit the concept "Songs made with or by Rush or members of Rush, yet never released by Rush". When it comes to guest appearances where a member of Rush did several songs I break them up. It sounds better to get a variety mixed in so, for example, you will find that a Platinum Blonde song is not followed by yet another Platinum Blonde song even though Alex played on two songs from the same album. Same for Jeff Berlin. Hopefully this will provide the most enjoyable listening experience.