That's fine for copyright on the music itself, but I think OPs concerns are probably about content matching which would disrupt the webcast. For example, if you were to stream Bach's
Jesu, Joy Of Man's Desiring performed by the New York Philharmonic, you could get hit because their recordings
are under copyright despite the song being public domain.
I believe content matching is based more on the performance than the song itself. I've seen some YouTube channels skirt the content match issue by using unpublished live performances for their teaching or critique, rather than the well-known recording done under a record label.
The Choir on Temple Square does a number of DVDs and CDs that are under copyright and managed by their label. But I doubt if the church has submitted General Conference into any content matching system. That would explain the guidance I got to only use performances from General Conference. So, you should be able to use anything found in
Conference Music without any issue.
That said, I know my ward streams sacrament over YouTube and plays hymns from the Sacred Music app (the local government doesn't allow singing in church - at least not without a lot of restrictions). They've not had any issues, but I'm not sure who owns the copyright on those performances.
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