Ok, You won't like the next one but I'm personally interested on this, so let me insist and introduce the new Electronic sub-genre
synthwave like this:
Electronic
Synthwave · Vaporwave
Synthwave::genre
Cyberpunk::genre
Darksynth::genre
Outrun::genre
Minimal synth::genre
Spacesynth::genre
Vaporwave::genre
Let me elaborate a bit, english in not my native language but I'll do my best. All these genres are already included, I'm only moving them. The synthwave genre is pretty well defined both temporally and "sensorially": Mainly made of synths, often by a single artist, with strong 80S sounding and/or themes taken from the pop culture of those years.
It originates from
French electro::genre and
Italo-disco::genre already included in the list, and to me it deserves a "sub-genre" promotion. Infact, they all share a similar temporal context (2010s) and synth-based origin; Even if it may sound a naive consideration, also the album covers of these sub-genres are significantly representative of it: skull and gloomy for darksynth, spacey and alien-like for spacewave, cars and beaches for outrun and so on.
On music streaming platforms these same defined genres are often grouped under the broader synthwave, suggesting a similar hierarchy. See other examples on
RYM or
Reddit.
I understand that these references may not sound academic but watching at other 3rd level sub-categories, like
Psychedelia or
Industrial · Noise for example, I still feel Synthvave deserves the same, as depicted on musicmap.info, too (where the sub-genre is Downtempo though: if you prefer we could name the 2nd level category like that instead of the proposed one