Wait, I think I know. The ISWorld in the file MIGHT be an outdated version -- because Chaotic 4, and the two ISWorld levels in Set #4 all use the new music, and the old ISWorld style doesn't have this song. I'll need to upload the new ISWorld soon.
"Stairway To Somewhere" was, I think, the 3rd to last level in the first set of my notebooks. However, the last level was never used in this set* (Because it is a bit too similar to a couple levels later in the set, like A Towering Proposition, and "Honey, I Shrunk the Levels" [Which I've yet to re-make, but it goes in the middle of Set #4]) -- And the second to last level was the level that is now "The Rainbow Road" and I moved that one to Set #2, replacing the second to last level with 4 Pillars and a Trap, which was initially Difficult 23. Still other levels in my notebooks do not work in Cheapo. For example, a one of each task replica of "Keep your Hair in Mr. Lemming" (now with the "mine on steel to turn" trick removed) cannot work because the miner and bomber task work differently. I did a lot of moving levels around for my sets, and removed a lot of the levels whose solutions were too similar (That is, were superfluous). I've only got about 10-15 actual levels in my notebook to re-create... The other 25 or so will need to be designed on the spot. Maybe I can try and alter some of the levels I'm not using to make them unique.
*Think "Origins and Lemmings", but with only climbers, floaters, miners, and diggers given to you.