Before Linked Horizon, known to international anime fans for the "Attack on Titan" openings, there was Sound Horizon
Before Linked Horizon, known to international anime fans for the Attack on Titan openings, there was Sound Horizon, described as "a group of artists led by the sound creator Revo (songwriter, composer and arranger). In order to express a fantastical story musically, he gathers and organizes suitable artists, without restrictions with regard to the number and sex of singers and storytellers."
In recent years, their narrative albums have been turned into manga, including one of their 2014 10th anniversary projects, Vanishing Starlight, the first volume of which will be collected in Japan on August 26th. To promote the release, Yuki Kaji (Attack on Titan's Eren) has narrated a commercial.
Ako Arisaka, who has also done an adaptation of Nein - 9th Story, as well as illustrations for the Yume Nikki novelization. illustrates the manga running in Shounen Ace.
Kamikaze Douga, of Jojo's Bizarre Adventure opening fame, animated a music video for the album when it was released.