Denpa song (電波ソング?) is a type of Japanese music that is intentionally strange and . Common features of denpa songs include intentionally off-key vocals, nonsensical lyrics and an over-the-top tune. Denpa music has grown into a subculture within Japan, forming a significant aspect of otaku culture and has large numbers of doujin circles and music artists dedicated to denpa music. Denpa is not a specific genre in itself, but rather an umbrella term for various kinds of music.
Alternative terms for denpa music coined in recent times include Akiba-pop and A-pop. The term Moe song (萌えソング?) specifically refers to denpa music of otaku origin featuring moe themes.
The term denpa song is a slang term that describes quirky, weird music. The term "denpa" (電波?, "electromagnetic waves") originally arose in the 1990s to describe quirky individuals who often daydream and live in their personal fantasies, and derives from the in 1981. The assailant, Kawamata Gunji, was using illicit substances when he slashed random bystanders in broad daylight, killing two housewives and two toddlers, and injuring many others. When confronted in court, he explained that electromagnetic waves (denpa) were telling him to kill people, and pleaded insanity. By the early 1990s, the term "denpa" began to appear throughout music and literature, and the phrase "denpa-kei" (電波系?) was used to describe delusional, creepy people or crazed lunatics as a derogatory euphemism, based on the idea that such people could hear voices, see things and communicate through telepathy as a result of electromagnetic waves. Examples of such usage at the time include songs by the Japanese metal band KING-SHOW which made references to the murder incident.