1. A system for delivering advertisements associated with styles of media content, comprising: a media server including a microprocessor, and a media server application executing thereon and adapted to receive requests from media devices for media content, wherein the media server is adapted to provide the media content in response to the requests from the media devices; a media style repository that stores metadata associated with items of media content, the metadata comprising one or more analytical and descriptive data describing at least one of a tempo, genre, or mood of the media content to be provided to the media devices; and wherein the media server, during streaming of a media stream which includes particular items of media content, from the media server to a media device, evaluates in real time during a period of play, at least one of the metadata associated with the particular items of media content that are being provided in the media stream to the media device, or a context associated with the media device or the user thereof, and uses an evaluation of the at least one of the metadata or context, to select a subject matter and a style of an advertisement or other sponsor-directed content to be delivered within the media stream in conjunction with the particular items of media content, based on one or more weighted characteristics associated with the at least one of the metadata or context, including one or more of a tempo or genre of the media content being provided during the period of play, including wherein the subject matter is selected based on a first weighting applied to a first set of weighted characteristics associated with the at least one of the metadata or the context, and wherein the style is selected based on a second weighting applied to one of the first set of weighted characteristics associated with the at least one of the metadata or the context, or a second set of weighted characteristics associated with the at least one of the metadata or the context.