Dolby is a brand name that became the everyday word for a system that cuts unwanted noise — the hiss and rumble — when you record or play music and film. Ray Dolby built the first famous version for tape in the 1960s; old cassette decks had a Dolby switch. Later the same name covered cinema sound (Dolby Digital, Dolby Atmos): not only less noise, but clearer, bigger sound in a theatre. People still say a film is “in Dolby” the way they once said a tape had “Dolby on.” It is a proper name, so it keeps a capital D. It is not a style of music, and not a kind of speaker by itself; it is the process (and the company) sitting on top of the recording.