Wiktionary
n. 1 Any music played in a public space whose main function is to create an atmosphere suitable to a specific occasion, rather than to be listened to. 2 Any music in a film, video game(,) or other medium that establishes mood and is not meant to have the audience's focus.
Wikipedia
Background music refers to various styles of music or soundscapes primarily intended to be passively listened to. It is not meant to be the main focus of an audience, but rather to supplement that which is meant to be focused upon. Music that is played at a low volume and is not the main focus of an audience is also referred to as background music. Traditional examples of background music include music played at various social gatherings and music played in certain retail venues. It is also common to employ background music in various electronic media including film, television, and Internet videos such as video blogs.
Background Music is the debut studio album by the American hardcore punk band Give Up the Ghost. The album was originally released on June 12, 2001 through Equal Vision Records under the name American Nightmare, but was later reissued in 2003 under the name Give Up the Ghost after another band named American Nightmare filed a cease and desist order. Background Music was also reissued in 2011 through Deathwish Inc. in celebration of the band's reunion shows.
Usage examples of "background music".
The mall had a mainly nostalgic appeal, and in any case, it was like background music: she could absorb it without really noticing it.