Hardtekk is a genre quite popular in Germany. Its know for having not much melodies, being repetitive and using a lot of distortion so that everything sounds a bit cheap. It is also quite popular in combination with German rap.

Speedcore is techno with 400+ bpm and Extratone is everything above 3600 BPM. This is The Rate at which the beats turn into a single tone and you can’t hear the single beats.

Hardcore is the evolution of Gabber with harder kicks and a usually darker theme. Nowadays hardcore is heavily influenced by Uptempo. This is why I prefer the old school hardcore over the newer stuff (Uptempo is cool, but I want to listen to hardcore but Uptempo light).

Another genre I like to listen to is terrorcore which is insanely brutal underground hardcore.

Examples for Hardtekk:
https://www.youtube.com/watch?v=Wqu8LHByWRI
https://www.youtube.com/watch?v=x-ZTVw2R9wA

Examples for Melodic Extratone:

https://www.youtube.com/watch?v=-AH4khgBBpY
https://www.youtube.com/watch?v=8HaK_MR0KXg

Examples for Extratone:

https://www.youtube.com/watch?v=kkivY3wwQHc (this one is technically Splittercore, but it does has good Extratone elements)
https://www.youtube.com/watch?v=i85jXEhukz8 (the end is Extratone)

Examples for speedcore in general:

https://www.youtube.com/watch?v=mOU4WDMchMY (check out the part starting at 4:20 that shit is sick)
https://www.youtube.com/watch?v=9pRpkbJdqVg

Examples for oldschool hardcore:

https://www.youtube.com/watch?v=bkj_kC8C8gU
https://www.youtube.com/watch?v=SLW5ijGIAaI

Examples for terrorcore:

https://www.youtube.com/watch?v=p1BefX-yt4k
https://soundcloud.com/iamglump/glump-on-top

Speedcore and Extratone are devinetively nothing that’s gonna become mainstream, but it devinetively doesnt deserves the hate it gets.