System, method and computer program that encompasses one or more client devices cooperating with a program host's on-line data processing center to generate media playlists. Data is transmitted from a program participant's client device to the processing center and is representative of media inventory in a media library on the client device and includes identification data of contained individual media items. Data is further received from a plurality of program participants representative of each respective program participant's media inventory, regardless of the source of the members of the inventory. Co-occurrence of pairs of individual media items in different program participants' media libraries is determined and a similarity rating is assigned between the pairs of individual media items based on the determined incidence of co-occurrence in the different program participants' media libraries. From this, a media playlist is generated.