It would be nice to have an option, when creating a pack, for the musics to rotate in the same way as in Mac Lemmings, i.e. if a rank ends on track 7, the first level of the next rank has track 8, instead of going back to track 1 with each rank as NL currently does. The disadvantage of NL's system is that some tracks end up playing half as often as others, and since everyone has their own favourites, it's no fun if your favourite is one of those.

We discussed this in chat just now and at least one other person would also like to have such an option

Wait, are we implying DOS Lemmings works differently?  I was under the impression that the so-called "Mac-style" rotation is standard across most ports of Lemmings 1.  I'm pretty sure you don't revert back to Track 1 in PC DOS Lemmings going from Fun 30 to Tricky 1.  It'd seem NL may be the lone oddball here.

Hmm, clearly I need to go fire up some emulators and try it out. I don't remember Genesis as being "arbitrary" for example, though to be fair, most of the time I probably wasn't playing those levels sequentially and weren't paying huge attention to the music.

Yeah, that's Genesis. "Random" isn't quite the right word, but instead of a rotation or any other regular pattern, each level has a particular music but those choices are jumbled up. Some tracks occur much more often than others. However, there is some more pattern, such as repetition of subsequences, than you'd expect from a random selection.

The original legit DOS verison works that way; it's not an emulation issue. Some later versions don't have the reversion to Lemming1, but still work on "first level you play in a session has Lemming1, then it moves to the next track each time you complete a level". This happens whether it's the next level or not; ie: if you were to complete Fun 1, then exit to the main menu and enter the code for Mayhem 30, you'd get Lemming2.

Special graphics levels do not cause skipping a track, nor do they revert to Lemming1 on failure. They're essentially completely seperate.

Implemented this for next update. It's the default option for new packs, but will not be automatically applied to existing ones.