Shan'tee

The Shan'tee were a race of conceptual beings native to the planet Wupatki.

Biology
The Shan'tee were, according to the Tenth Doctor, made up of the "incomprehensibly tiny mathematical shifts in quantum foam, only they don't need to be observed, they need to be heard." Normally, they manifested to humans as beautiful, living music. They were also genderless in human terms.

They could be made visible to humans via a visual translation matrix. This way, they appeared as a floating, vaguely humanoid-shaped mass of mist of various colors such as pink, purple, red, green, etc. with a mask that served as their "face".

Individual Shan'tee could duplicate themselves through a method of procreation that few Shan'tee were schooled in. This technique was only used in times of trauma.

The Shan'tee's natural habitat was the oxygen-rich layer of the Wupatki gas giant. Being essentially living songs, they needed an atmosphere to survive. If they were caught in an environment low in oxygen, their bodies would lose cohesion, effectively killing them. (COMIC: The Singer Not the Song)

Abilities
Shan'tee could manipulate sound for various purposes. They could render people unconscious by cutting off all auditory stimulation, effectively "deafening them with silence". They could also mimic frequencies of higher intensities such as the Doctor's sonic screwdriver. Using this technique, they could disable machinery such as robot drones. (COMIC: The Singer Not the Song)

History
The Shan'tee were natives of the habitable layer of a gas giant called Wupatki. At some point in the far future, humans colonized the planet and built a network of cities around it. Both races coexisted and Wupatki became a peaceful trading post with other human colonies.

The Tenth Doctor and Gabby Gonzalez visited Wupatki and met the native species. They soon learned that a Nocturne virus was being sent to the planet and was turning the otherwise peaceful Shan'tee into monstrous killers. The Doctor discovered the virus had been transmitted on songs broadcast from a space radio station by an unknown party. He travelled to the station and stopped the transmission of the virus before emitting the normal version of the song that cured the Shan'tee of their infection. (COMIC: The Singer Not the Song)