The Sama Veda has 1,875 mantras, the majority of which are from the Rig Veda. The Panchavimsha, and Shadvimsha Brahmanas, the Tandya, Chandogya and Kena Upanishads were a development from the Sama Veda.
The Sama Veda gained importance and prominence because Bhagwan Krishna said in the Bhagavad Gita (10.22), "I am Sama Veda among the Vedas."
The special priest of Sama Veda is known as an udgata. He is an expert singer who invites the devas by singing the mantras to entertain and please them.