Anime music falls into several distinct categories with different commercial and artistic functions: the background score (BGM); the opening (OP) and ending (ED) sequence songs; the insert song (sashikomi-kyoku); and the image-album track. Each is commissioned and recorded under different conditions and contributes differently to the production's identity and revenue.
Background score (BGM)
The score for a TV anime is typically commissioned from a single composer who delivers a set of cues — often 30 to 60 tracks — recorded as an ensemble session in the months before broadcast begins. The episode director and the sound director (音響監督) select tracks from this menu episode by episode. Composers consistently in this role include Yoko Kanno, Yuki Kajiura, Yasuharu Takanashi, Kohta Yamamoto, and Hiroyuki Sawano.
Opening and ending sequences
The OP and ED sequences — typically 90 seconds each — function as both story-internal credit sequences and as standalone music releases. They are usually commissioned from established pop, rock, or visual-kei artists, and the resulting singles often outsell the anime's other merchandise. Some long-running series (One Piece, Detective Conan) rotate OP and ED songs at season boundaries or arc divisions.
The image album
An 'image album' (イメージアルバム) is a record released alongside an anime or sometimes before it, containing songs and instrumental pieces not used in the production itself — character themes, story-inspired songs, or compositions that influenced the final score. Joe Hisaishi's pre-production image albums for Studio Ghibli productions are the canonical example.