was a Japanese composer

Composer

A composer is a person who creates music, either by musical notation or oral tradition, for interpretation and performance, or through direct manipulation of sonic material through electronic media...

 and guitarist

Guitarist

A guitarist is a musician who plays the guitar. Guitarists may play a variety of instruments such as classical guitars, acoustic guitars, electric guitars, and bass guitars. Some guitarists accompany themselves on the guitar while singing.- Versatility :The guitarist controls an extremely...

 known for creating melodies, and a pioneer of Japanese popular music. He was regarded as a notable figure for establishing the genre enka

Enka

is a popular Japanese music genre considered to resemble traditional Japanese music stylistically. Modern enka, however, is a relatively recent musical form which arose in the context of such postwar expressions of modern Japanese nonmaterial nationalism as nihonjinron, while adopting a more...

, though Koga considered that he was a ryūkōka

Ryukoka

- 1914–1927: Origin :In 1914, Sumako Matsui's song "Katyusha's song", composed by Shinpei Nakayama, was used as a theme of the rendition Resurrection in Japan. The record of the song sold 20,000 copies...

composer. He wrote numerous songs for Ichiro Fujiyama

Ichiro Fujiyama

, born as , was a popular Japanese singer and composer, known for his contribution to Japanese popular music called ryūkōka by his Western classical music skills. He was born in Chūō, Tokyo, and graduated from the Tokyo Music School. Although he was regarded as a tenor singer in Japanese popular...

 and Hibari Misora

Hibari Misora

was an award-winning Japanese enka singer and actress. and was the first woman in Japan to receive the People's Honour Award, which was awarded posthumously for her notable contributions to the music industry. Misora recorded 1,200 songs, and sold 68 million records. After she died, consumer demand...

, and his work has been featured in various films, including Come See the Paradise

Come See the Paradise

Come See the Paradise is a 1990 film directed by Alan Parker, starring Dennis Quaid and Tamlyn Tomita. Set before and during World War II, the film depicts the treatment of Japanese people in America following the attack on Pearl Harbor, and the subsequent loss of civil liberties within the...

, and Memoirs of a Geisha

Memoirs of a Geisha (film)

Memoirs of a Geisha is a 2005 film adaptation of the novel of the same name, produced by Steven Spielberg's Amblin Entertainment and Spyglass Entertainment and by Douglas Wick's Red Wagon Productions. It was directed by Rob Marshall. It was released in the United States on December 9, 2005 by...

. He was the head of the "Japanese Society of Rights of Authors, Composers and Publishers" from 1964 to 1978. A museum was built in Shibuya

Shibuya, Tokyo

is one of the 23 special wards of Tokyo, Japan. As of 2008, it has an estimated population of 208,371 and a population density of 13,540 persons per km². The total area is 15.11 km²....

to honor his achievements, and visitors to the are able to view exhibits, and memorabilia featuring his work.