A Midsummer Night's Dream 5.1 Performance: Titania and Oberon Lines 383-392

The transcript describes a magical scene where elves and fairies gather around a fire. They engage in a lively dance and song, rehearsing their tunes and blessing the place with their enchanting presence.

What is the purpose of rehearsing the song by rote according to the text?

In what way does the text suggest that the song should be performed?