I had one more crash mid-day today, again while running audacity. It was definitely audacity that first hung -- the pavucontrol window was still working, and I had time to open a terminal and kill the audacity process. But it all went south a few seconds later, and even magic SysRq couldn't reach it. I looked at syslog and kern.log. In kern.log there were a lot of ATA errors, beginning with "ata12: log page 10h reported inactive tag 26" which google says are typical when the systems stops addressing the drives -- I think that was a symptom, not a cause -- my drives are new. But nothing in syslog.
