Tunes & Tales, Modeling oral transmission

Oral transmission is a fascinating aspect of the broader phenomenon of cultural transmission. In oral culture, artefacts such as songs and stories are passed on to next generations without written or technical reproduction media, just by voice and ear. Oral transmission implies alteration and variation to a considerable extent. Yet after several generations of oral transmission the artefacts are still ‘the same’ (in oral terms), or at least recognizable variants (from a literate point of view). How can this be? Are there convergent forces? How can we model the process of oral transmission?