I have just heard - for the first time - The Taneyev Quartet performing, or attempting to perform, the Eighth and Ninth Quartets of
Sergei Taneyev.This is not the edition I have, but here is a newer picture of what they are selling:

If you want to hear
wavering microtones in these quartets, as if
Taneyev had cosmically pre-channeled
Bartok and maybe
Penderecki, then this is the CD for you!

There are spots in the slow movement of the
Eighth Quartet where I thought an
Alois Haba quartet had been spliced in suddenly!
Apparently intonation is a problem with the group on these recordings: I found some reviews complaining about the same thing on other quartets.
Let's hope the new NAXOS survey of
Taneyev Quartets will not show similar unintended experiments in quarter-tones!
