Maybe also disable notifications from Settings and Security and Maintenance. Or just disable playing a sound when notification arrives.

Yep, I had already done that but they kept coming. I suspect I'm paying the price for being lazy and not doing a disk wipe and bare-metal reinstall of Windows on my laptop when I first got it. It's a Lenovo, and I'm starting to think their bloatware is overriding the Windows settings somehow and playing these sounds whenever it sends a notification. I can try uninstallling the Lenovo tools, and if that doesn't solve the problem I'll wipe and reinstall. I'm at my limit on Pianteq installs, though, but presumably it's locked to my machine and not the OS so if I reinstall Windows I'll still be able to install Pianoteq.

I did get this machine with the idea of eventually turning it into a Linux-only laptop, as I'm comfortable in Linux, but want to use Windows for now for a variety of reasons.

This is the Focus Assist feature in Windows. Set that to "Alarms only".

This actually didn't work, surprisingly enough! I set it to alarms only and 10 minutes later up came a loud chime with the computer telling me I needed to install a bios update. So I set the sound scheme to "no sounds" and we'll see if that works. Fingers crossed, as I have a concert coming up in a little over a week.