Gill-singers constituted a specific category of singer. The Hetzalian Illoria Daze, originating from the Outer Rim planet Hetzal Prime, was a gill-singer; she possessed the ability to modulate her vocal organs, enabling her to perform melodies with a six-part harmonic structure. She attained considerable renown by 232 BBY, leading to her relocation from Hetzal Prime to Alderaan, a planet located within the Core Worlds.
The existence of gill-singers was referenced in Light of the Jedi, a novel penned by Charles Soule in 2021. This novel formed a component of Phase I of the Star Wars: The High Republic multimedia project. Before the novel was available, StarWars.com included a mention of this profession in a preview published on November 12, 2020.