Sound non-functional on Lenovo P50 running Mint 18 after failed update
 

OK folks, I'm using a Lenovo P50 laptop running Mint 18 x64 Cinnamon.

Sound worked fine for the last couple months, then just today it stopped working. I noticed when installing some updates that one of the packages failed to download. It was an audio related package, I think it was "oem-audio-hda-daily-dkms". Interestingly though that package has disappeared from the Update Manager since I rebooted (other updates installed fine). That makes me think that it ended up installing successfully after all.

I tried switching the audio driver in the Driver Manager (two options are oem-audio-hda-daily-dkms and oem-audio-hda-daily-lts-xenial-dkms and restarting but no change. Also tried switching back to the original.

Alsamixer shows speakers are not muted.

Any tips?

OK here's a complication.

When I hit the volume up or down function keys, I can hear the Mint action sound, but that is the only sound I've been able to get out. Spotify does not output sound, nor does Youtube or Vimeo.

I remembered I had set my Display option to "Discrete Graphics" in BIOS.... changing it back to "Hybrid Graphics" fixed the sound issue.