We have the metal thread and the electronic music thread, so now here's the thread for all sorts of experimental rock music, including but not limited to avant-garde, fusion, improv, "prog", Krautrock/Komische, RIO, zeuhl, post-rock, math rock, industrial, and anything else ostensibly rock-based that strays from the beaten path and isn't better classified as metal.
So, full disclosure. During late high school and early college, I went through a serious "prog" phase. It was nearly terminal. Only through significant musical therapy did I recover. Many years removed from the affliction now, I have begun going back through my collection and finding what still holds up and what was the disease talking.
Let's start with the Japanese fusion band Kenso.
They've been around for a long time, though a lot of their stuff is Japanese import only. "In the West" is generally easy to find (it's on Spotify and GPM) and really good, though I prefer the rather difficult to find "Ken-Son-Gu-Su". Their live recordings are preferable to their studio albums, including one of my favorite album names ever: "Music for Unknown Five Musicians".