In the continent of Polyphonica, spirits materialize in the world, surviving on the music that is played by humans, and live together with them.

Musicians called Dantists (神曲楽士, Shinkyoku Gakushi) play Divine Songs (神曲, Shinkyoku, also "Commandia") using special instruments called One-Man Orchestra (単身楽団, Tanshin Gakudan) which enable the spirits they have partnered with to manifest their true powers.

The Crimson series follows the adventures of a Dantist named Tatara Phoron and his contract spirit Coathicarte Apa Lagranges (Coatie).

Written by Ichiro Sakaki and illustrated by Tomo Hirokawa, a manga series adaptation entitled Cardinal Crimson (カーディナル・クリムゾン, Kādinaru Kurimuzon) began serialization as a web comic in March 2007 in FlexComix Blood[citation needed] and ended in 2012.

T.O Entertainment adapted Shinkyoku Sōkai Polyphonica into a twelve episode anime series directed by Junichi Watanabe and Masami Shimoda and written by Ichiro Sakaki.

Diomedéa adapted the series into another season entitled Shinkyoku Sōkai Polyphonica Crimson S, directed by Toshimasa Suzuki and written by Ken'ichi Kanemaki, that is not a continuation of the first and will tie into Ichiro Sakaki and Noboru Kannatsuki's light novel adaptation of the same name.

The Shinkyoku Sōkai Polyphonica anime series was licensed for distribution in North America by Sentai Filmworks.

[11] The second season prequel series Shinkyoku Sōkai Polyphonica Crimson S was licensed for distribution in North America by Maiden Japan.

A complete DVD collection titled Polyphonica Crimson S, containing all 12 episodes, in Japanese language with English subtitles, was released on April 3, 2012.

A Shinkyoku Sōkai Polyphonica RPG, published by GA Bunko, went on sale in Japan in August 2008.