Mac Mail app plays additional, unwanted "Mezzo" alert sound

No matter how I set "New Messages Sound" in Mail Settings, I also hear the "Mezzo" sound whenever new mail arrives. For every message there are two sounds—what I select AND Mezzo. (If I select Mezzo as my new mail sound do I not get two alerts, just the Mezzo once.) But I dislike Mezzo and want only the sound I prefer. I have booted into Safe Mode and nothing was different. How can I maintain my notifications but stop Mezzo?

Thank you.

Mac Studio M2 Max

macOS 13.5.1 Ventura

Mail 16.0