Definition of the cyberpunk genre?
How is the cyberpunk genre defined?
Some musicians and acts have been classified as cyberpunk due to their aesthetic style and musical content. Often dealing with dystopian visions of the future or biomechanical themes, some fit more squarely in the category than others.
I understand that a song belongs to the cyberpunk genre if its lyrics are about cyberpunk topics, but what about the actual music, e.g. instrumental works? What is this "aesthetic style"? How does cyberpunk sound?
'Cyberpunk' is a primarily a visual and literary genre, and cyberpunk music (as you mentioned) could be any music that displays synergies with cyberpunk's key topics of technology, industry and 'griminess', alternative culture, dysfunctional society, and so on.
Because of the technological aspect, a large swathe of techno / electronica music could be considered 'cyberpunk' as soon as someone chose to draw the association. The griminess/social breakdown aspect also encourages incorporation of industrial and other techno-influenced rock bands. Such 'human-fronted' acts also have an obvious parallel with one focus of cyberpunk : The effect of technology on people.
So musically, 'cyberpunk' is (for now) a catch-all term for a range of existing genres, particularly techno, industrial, and industrial rock.
When I was really into the cyberpunk thing in 94-97ish there was never a section in the record store called 'cyberpunk', but me and all my leather clad, cyberpunk novel reading friends (we just called ourselves punks, or rivet-heads, not cyberpunks) were really into industrial music which at the time included bands like Babyland, Front 242, Chemlab, and of course Front Line Assembly. Also some older industrial stuff like Einstürzende Neubauten and Nurse with Wound.
Front Line Assembly really defined 'cyberpunk' to me. Check out this album, I mean it's called Tactical Neural Implant, it's like a line right out of a Gibson novel.
Cyberpunk isn't a musical genre but it is an visual/dress aesthetic that might be selected when going to a punk bar or a rave. Cyberpunk does have its origins in Western Canada so bands from Vancouver were the first to really grok the themes behind William Gibson's works. That included Skinny Puppy (who were more interested in exploring body horror) and Front Line Assembly (who definitely characterised the sound of cyberpunk musically.)
Body horror is a significant field of exploration so while punk is often associated with hard and fast music, Skinny Puppy, Moev and FLA went the route of Suicide: slow, brooding, disoriented, depressed and rebellion within that trapping. That said, the main field of exploration is cyberspace and digital interfaces. So while industrial rock deals with body horror, its treatment of interfacing with cyberspace occurs much less.
Very good album to look at:
Sect - Telekinetic  (side project of FLA)