This is a Chinese verse, which means: After an ancient song is played, the moon on the autumn river rises, and thousands of dances begin at the same time, as beautiful as the blooming jade tree.
The "sound of ancient ending" in the poem refers to the end of an ancient song played, and the "Autumn River Moon" means that it is autumn at this time and the moon has risen. "Ten thousand dances bloom together" describes the dance scene as spectacular, as beautiful as the blooming jade tree. The whole poem depicts a very spectacular scene, showing the author's love for music and praise of dance.