Do you think the song “Pioneers Over c” by Van Der Graaf Generator could be considered filk? It’s prog rock rather than folk, but it is about the first astronauts to surpass the speed of light, who then find themselves sort of disconnected from time. I suppose it’s more like speculative fiction in song form than science fiction fandom, though. Idk, that’s why I’m asking y’all.
It is if you want it to be! Because definitions are made up and only exist as long as they are useful to us. I definitely thing filk is a genre doesn’t ever need to sound folk-ish, it just often does because 1) it evolved out of the 60′s folk movement and 2) it’s an easy style to write and perform in for amateur musicians. But heck, there’s rap filk, there’s no reason there should be prog rock filk…except that prog rock typically requires at LEAST six musical instruments and electricity, and so is more conducive to staged concerts than song circles.
….but there’s plenty of filk on concert stages, with electric instruments, with the extensive arrangement, rehearsal, and setup you get in prog rock. I saw a prog rock band at a con, and while it wasn’t billed as filk, being at a con makes you basically filk.
As for whether it’s science fiction fandom music – if you’re in the science fiction fandom, and feel like it’s relevant, and you like it, it’s science fiction fandom music. That’s why songs about cats and Shakespeare are considered filk, even though they have heck all to do with science fiction. They might be pretty far removed from Star Trek, but a whole bunch of people like all of those things, and that unites them. Fandom is about the people, more than the content, in the end.
Anyway, I’d say a case can be made for calling it filk, and if you want to make that case that’s fine by me. It’s a few steps removed from what I might suggest as some kind of archetypal filk song, but that doesn’t mean it isn’t one. It’s like how a dachshund and a wolfhound are both dogs. They’re just very different dogs, and you just have to be aware that traits of most dogs do not necessarily apply to these dogs. If filk had a real dictionary definition it would have a dozen subdefinitions, and one of those would probably say “songs about science fiction concepts” and that’s this!