What do the three tones in poetry mean?

The tone, artistic conception and diction are all the same. The three tones of poetry refer to the principle of poetry creation put forward by Bai Juyi, a poet in Tang Dynasty, that is, "the sound, artistic conception and diction are consistent". This means that the musicality, imagery and expressiveness of poetry should be coordinated with each other to achieve a harmonious effect. This principle is widely used in Tang poetry and has become one of the important features of Tang poetry.