Ben Johnston's most famous string quartet is easily No. 4, his variations on "Amazing Grace". Someone posted a video of a recording with a read-along score.
At 5:59 your eyes won't deceive you, the time signature really is 9/64. I'm fond of Variation 7. What I like about Johnston's music is there where in one realm he pushes along within avant garde ideas (a different tuning system for every variation on "Amazing Grace", if memory serves), he has a countervailing impulse that balances out the avant garde with something accessible, which in this case is, obviously, doing microtonal extended just intonation variations on one of the most famous hymns in the history of the United States.