A method of indexing recordings of contact center communication sessions is described. The method allows for a recording to be indexed with metadata reflecting a time-varying characteristic of one or more of the parties of the communications session, e.g. the mood of a caller, the current location of a caller. The indexing of recordings with such information allows for more granular search of recordings, in order to find particular call conditions. This can be useful from the point of view of education and training of new call center operatives, and for assessment of call center performance.