[alsa-devel] Unknown PCM cards.pcm.front

In my custom cape for Beaglebone black, I'm able to play audio reasonably well. But for one situation when my C++ app (which plays via libao) opens an output, this is written to my app's output:

"ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.front"

Googling, I found this advice:

http://alexpb.com/notes/articles/2012/11/14/error-when-playing-audio-on-rasp...

Which works.

My question is, why do I get it only in this instance? Is it because I might be opening the audio device twice simultaneously? That's about the only thing that might set this situation apart from all the others.

TIA,