Seg fault on 2nd thread?

error.txt

^C
KeyboardInterrupt detected. Signaling threads to stop...
^CTraceback (most recent call last):
  File "/Users/gene/sandbox/Music/midi-threads.py", line 44, in <module>
    time.sleep(0.5) # keep main thread alive and respond to interrupts
    ~~~~~~~~~~^^^^^
KeyboardInterrupt

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/gene/sandbox/Music/midi-threads.py", line 47, in <module>
    clock_thread.join()
    ~~~~~~~~~~~~~~~~~^^
  File "/opt/homebrew/Cellar/[email protected]/3.13.7/Frameworks/Python.framework/Versions/3.13/lib/python3.13/threading.py", line 1094, in join
    self._handle.join(timeout)
    ~~~~~~~~~~~~~~~~~^^^^^^^^^
KeyboardInterrupt
Segmentation fault: 11