[js_nyc]

Thanks for your reply, OD. I do understand your thinking and the principles of "sharing audio core" (even on a Mac), but I only went to System Preferences after Pro Tools had shown a grayed out Thunderbolt Native Ultimate display under the Playback Engine options. Just wanted to check if the Thunderbolt Native card-to-interface even showed up as an option for Sound Output. Did Not have Thunderbolt set to Output initially- it was on either Built-in speaker or Headphone out. But it did show up as an option, so then I tried it to see if any other App would play through (which they did). So thanks again, but this is not the solution.