I wanted to report back on progress so far.
Summary:
emptying the MC library completely, then rebuilding it from scratch, seems to have stopped the problem. I have no clue what caused the problem or why this action seems to have fixed it, but after about a day I'm still able to play music for an unlimited amount of time without MC halting.
I looked into JimH's suggestions, but nothing came of them as far as I could tell. Among other things, I don't have any NVIDIA hardware or software that I can find, so that issue doesn't seem to have been the cause.
I was unable to duplicate the problem with Windows Media Player (win11 pro) or the free version of Media Monkey. Both played for as long as I let them without interruption.
I tried uninstalling, then reinstalling MC. Same behavior.
I tried disconnecting, then reconnecting, the USB drives on which I keep my audio files. No change observed.
I rebooted a couple of times. No joy.
Then, by accident, something seems to have worked. I was maintaining my music files, cleared the existing MC library, and created a new sandbox library with just a few dozen files, including some of the files that had stopped abruptly before. Suddenly the fault I had been seeing before stopped happening. So I cleared the library completely and rebuilt it using all my recorded music files. Now, so far, after about a day, I haven't seen the player halt again.
This is a little frustrating because I can't induce the problem again, so I don't know what the cause is. But at least so far, I can listen to music again.
So, to esotericxa, try clearing and rebuilding your music library from zero. Maybe that will work for you.
I'll report back again in a few days to say whether I'm still able to play music files at will.
Thanks for everyone's help.