(play-sound) doesn't return a subprocess and doesn't exit with (exit)

[bluerider]

(play-sound) seems to spawn a subprocess but doesn't return the subprocess on Linux/Unix. In addition, the subprocess (aplay) doesn't kill with (exit) or (kill-thread) when run in a thread. A solution in #racket on freenodes advised to use (current-subprocess-custodian-mode 'kill) which allows it to kill the thread with (exit).