The term "sound novel" (サウンドノベル) originates from Chunsoft's popular Sound Novel franchise, which began with the Super Famicom release of Otogirisou in 1992, but eventually grew into a genre title that encompassed games from multiple companies that mimicked the style of storytelling used by Chunsoft.
Sound novels are an evolution of Japanese adventure games with their main characteristic being their focus on reading rather than problem solving, with text usually covering the entire screen and other visuals often being deemphasized or minimalist in style. As may be expected from the genre's name, sound and music are heavily used to immerses the player in the story. Interactions are limited to making choices that branch the story to a number of different endings although there are some titles that have linear narratives with no gameplay at all.
The genre was huge in Japan during the mid-1990s, exploding in popularity after the release of Chunsoft's Kamaitachi no Yoru in 1994, and seeing the most activity on consoles like the Super Famicom and PlayStation. The genre eventually moved to Japanese computers with Leaf's Visual Novel Series, which created the term visual novel, and eventually saw new life in the Japanese doujin scene during the early 2000s thanks to the popularity of titles like 07th Expansion's Higurashi. However, outside of Japan, the term "sound novel" is very obscure and seldom used since very few entries in the genre are available in English and because many of the games are simply reclassified as visual novels by western fans.
- Japanese Wikipedia Page