1. A method comprising: receiving, at a media rendering device, a request for a play list of songs in accordance with a mood of a user; retrieving, by the media rendering device and based on the user mood, a defined mood gradient comprising an identifier identifying a mood and a sequence of target value sets for the identified mood, each target value set including a plurality of values, the plurality of values comprising at least three values, each value in each target value set corresponding to a dimension of a multi-dimensional space in which at least one song is represented, the multi-dimensional space having at least three dimensions, each dimension of the multi-dimensional space corresponding to a different one of objective musical characteristics comprising at least tempo, brightness and beatedness, an objective analysis of audio data of the at least one song being used to generate the at least three values for the at least one song; for each target value set in the mood gradient, selecting, by the media rendering device, a song based on the at least three values in the target value set; and generating, by the media rendering device, the playlist of songs for playback, the play list containing each selected song.