The music is known as enka which was revived in the modern form around 1969. The style of enka refers to many aspects of traditional Japanese music blended with modern instruments which creates some interesting contrasts. Bamboo flute or Shakuhachi followed by piano, koto with oboe, electric guitar, sweeping strings, gypsy violin, folk guitar rythms, harpsicord and even sleigh bells. Most songs are sentimental ballads that draw on a traditional, idealised or romantisized aspect of Japanese culture and attitudes.
So why is Rumiko's singing replaced by a koto? It could be that the album was put together for an English speaking audience. The orchestral arrangements by Kenichiro Morioka are the actual backing tracks for Rumiko's hit songs. It would have been easy to find a musician to play koto - karaoke style.
Recorded in Japan
Arranged by Morioka Kenichiro 森岡賢一郎
Songs originally sung by Rumiko Koyanagi 小柳ルミ子
Songs written by Hirao Masaaki 平尾昌晃
Advent of Spring written by Koichi Morita 森田公一
A Folded Paper Crane written by Hama Keisuke 浜圭介
Tears of Longing: Nostalgia and the Nation in Japanese Popular Song