1. A method comprising: storing a plurality of mediasets for multiple different users in a knowledge base of mediasets; and preprocessing the knowledge base of mediasets to quantify an association between pairs of media items in the knowledge base, comprising: for each item in a mediaset, identifying every other item in the same mediaset, so as to define all of the pairs of media items in that mediaset; repeating said identifying step for every other mediaset in the knowledge base, thereby defining every pair of items that appears in any mediaset in the knowledge base; and for each identified pair of media items, adjusting a co-concurrency metric value responsive to each additional occurrence of the same pair of media items in the knowledge base, said co-concurrency metric value comprising a co-concurrency metric value being defined as a number of times that multiple media items appear together in multiple users' mediasets; receiving, from a client device, at least one input media item; identifying, from the plurality of mediasets for the multiple different users in the knowledge base of mediasets, a plurality of ordered pairs of media items containing the input media item; and selecting one or more of the plurality of ordered pairs of media items by determining that the co-concurrency metric value is adjusted above a predetermined threshold value.