In reality this hypothetical scenario is almost unimaginable. Once the choir director chooses a song and helps the choir rehearse they sing in beautiful unity. There is a wonderful message in this. Once the person with the authority to lead makes a decision, there is little to be gained from public discord. We might compare the choir to the ward council. The council meets together to discuss the needs of the ward. They contribute ideas and insight. The bishop listens carefully and learns from the members of the council. But, once a decision is made and the bishop signals that it is time to move forward, complaints and actions inconsistent with the decision made in council is much like singing a different song than the rest of the choir because you didn't get your way.
The lessons to be learned from music extend to singing hymns in sacrament meeting. Remember the Lord's statement on singing in D&C 25:
12 For my soul delighteth in the song of the heart; yea, the song of the righteous is a prayer unto me, and it shall be answered with a blessing upon their heads.Just as with the ward choir, it would be quite disruptive to sing a different song than the rest of the ward. We join in, not because the current hymn is our favorite or the one we would have selected, but because it is being sung in praise and worship. It is a unified prayer for the congregation and brings the spirit into the hearts of those attending. When we sing hymns we are experiencing a type of unity. There can be people in the congregation who have differences. They may even have hard feelings in some areas. Yet, while the hymn is being sung they are praying and praising God in unity, and being blessed for it. In a small way, the singing of hymns is an experiential lesson preparing us for Zion. As the Lord taught in Moses 7:
18 And the Lord called his people Zion, because they were of one heart and one mind, and dwelt in righteousness;The hope is that we can take the wonderful spirit and attitude of unity that we feel while singing hymns and extend that to all of our service to one another in the church. The singing of hymns is a type of experiential learning about Zion, where we will be of one heart and one mind. Learning this lesson will help us learn of Zion.