It's the StarTech sound card. When I plug my headphones directly into the NUC, Celluoid starts immediately without the silly extra tab. Thanks, Newegg, for selling me a used NUC when I bought a new one.

Thanks to everyone who responded.

@stultumanto "buffer overruns" Interesting, I will look into that. Something I did not mention, and it's probably important, is that my NUC arrived with a very loose 1/8" jack, so I use a Startech plug-in audio device (ICUSBAUDIO2D). It just occurred to me that it might be adding some unwanted effects. I will investigate.

@czeekaj I never heard of cmus. I installed it via Synaptic, but then it did not show up in the list of applications, though an mpv player did. I tried the mpv player and it plays WMA Lossless files with no delay or degradation. Maybe I found a new player.

By the way, the reason I have WMA Lossless files is that I'm a Windows refugee from way back, and I still rip music via a Windows platform. MP3 is not the same in terms of quality. I have a small number of FLAC files that I acquired via the purchase of classical music for which a CD was not avaiable.

Thanks to Dutch_Master (I think I saw you on a box of cigars) and aluma. Learning a new system is always interesting and it helps to know how to find help.