There are at least three bands/musicians using this name:
(1) Cornelius (born Keigo Oyamada (小山田圭吾 Oyamada Keigo) 27 January 1969 in Setagaya-ku, Tokyo, Japan) is a Japanese recording artist and producer. His name is a reference to the Planet of the Apes chimpanzee character of the same name played by Roddy MacDowall. Oyamada's first claim to fame was as a member of the pop duo, Flipper's Guitar, one of the key groups of the Tokyo Shibuya-kei scene. Following the disbandment of Flipper's Guitar in 1991, Oyamada donned the "Cornelius" moniker and embarked on a successful solo career, while also producing for Pizzicato Five.
Cornelius's musical style is often described as being similar to Beck's, whom he acknowledges influenced him along with The Beatles, The Beach Boys, The Jesus and Mary Chain, and Primal Scream, among others.
The music of Cornelius could be described as experimental and exploratory, and often incorporates dissonant elements alongside more familiar harmonically "pleasing" sounds. This tension, plus his practice of bringing in sounds and samples from mass culture, pure electronic tones, and sounds from nature (see his Point album) lead him to being sometimes categorized as an "acquired taste."
He chose his pseudonym in tribute to the character of the same name from the movie Planet of the Apes. He commissioned a song, about himself, on Momus's 1999 album Stars Forever.
Oyamada married fellow musician and collaborator Takako Minekawa in 2000. The couple later divorced in 2012.
(2) Cornelius is also an emotional/blackmetal/hardcore band from Mainz, Germany.
(3) Cornelius was also a mid-90's hardcore / emo band from North Carolina. They released a Discography, "Sounds Like Summer," on Assorted Porkchops. Recorded 1994-1996, .