I've mentioned before that there are some thematic worldbuilding similarities between Scylla and Charybdis and Surgeburnt: both are settings that have "recovered" from the apocalypse; both address a backlash against current society's constant connectivity; and both put physical books in an isolated but hallowed niche, primarily because I am a book nerd and have an undying love for ink and paper. I even posited a theory that they could be the same setting, since the planetary denizens in SaC have long since lost contact with Earth, and I haven't ruled out space travel in Surgeburnt, at least not explicitly. But that's a bit of silly fluff and I don't think I'd formalize it; the two settings *feel* very different to me in other ways, and to me they don't belong in the same universe.
But there is one more thing that is similar between them. I recently discovered that they both have the same song on their general theme list:
Children Of The Revolution - Kirsty MacColl
(This is Kirsty at her best, by the way: it's such bright, cheerful instrumentation and the lyrics are biting, snarky and dark.)
The song applies to my projects in different ways, but it is definitely appropriate for both.