With the advent of social media, we hear about these virtual choirs. Do Christians have the authority to do virtual choirs and post them on Facebook? Doesn't this constitute entertainment because they have an audience?
I can play the card game Solitaire and find it entertaining, even though there is no audience. A congregation jointly singing praises to God is doing so with an audience of themselves. Singing is fun but it is not done for the purpose of entertaining those attending worship but to fulfill a command of God (Ephesians 5:19; Colossians 3:16). Thus, whether there is an audience or not does not get to the root of the question.
If I sing hymns while putting shingles on my roof, would that be wrong? If my neighbors walked by, I would consider it a form of teaching others about the Bible, just in musical form. A recording of a hymn being sung can serve the same purpose, just without you being present.
The objection to choirs is in the use of choirs during worship. The music God commanded is for brethren to sing together while teaching each other through the words of the songs. What is found in many denominations is a soloist or choir singing to a passive audience. This is not the type of worship God commanded. It alters the command and, thus, becomes wrong. As a result, groups are chosen to draw crowds. The entertainment is valued far above obedience. The emotions created are valued above what is being taught by the words.
Virtual choirs among the brethren are Christians getting together to records hymns to teach people through song. It is not a part of a worship service to God. The singing makes the teachings memorable and might increase the likelihood of the hymn being shared with people, but the primary purpose is not entertainment. However, there is nothing wrong with good teaching being entertaining, whether by words or in song.