The dictionary definition of "ambiance" is: atmosphere: a particular environment or surrounding influence; "there was an atmosphere of excitement".
In sound terms, this could be the creation of music/sound which fits with the atmosphere in the scene at the moment. The music will create a certain feeling for the audience - for instance happy music will tell the audience how they should feel, that they should feel happy. The same goes for sad music, it will tell the audience to feel sad about whatever is happening in the scene. If the music does not fit, it could be considered contrapunctal or asynchronous.Ambiance can also include how the audience should feel about a particular character, especially if the characeter has a sound motif.
Look Up at the Stars, Portugal! from Matthew Brown (Matty Brown) on Vimeo.
I think this particular video has sad music and it is about a boy's life ending. The music is slow and fits well with the video.
Hello, I Like You from Mixtape Club on Vimeo.
This video is about happiness, and the music really reflects that. It is upbeat and cheerful and the audience can sit and watch what is happening on the screen while knowing they are supposed to be feeling happy about it.
