pilgrim,

The purpose of hymns is to teach and admonish. This includes hymns of praise. Col 3:16. When the flock is assembled for corporate worship, the authority to teach and admonish is given to ministers. 1 Cor. 4:1; Acts 20:28; Heb. 13:17.

As I said, single women may add their voice to the voice of the pastor. But, when single women teach and admonish on their own, they are usurping the authority of men.