What mechanisms allow birdsong cultures to accumulate, instead of collapsing into either high conformity or chaos? In the lab, the emergence of song culture can be studied by establishing a new songbird colony, starting with an isolated bird that never had an opportunity to learn a song from an adult tutor. This new song will be abnormal: isolated songs are often not even recognisable as belonging to the species. Juvenile birds, however, will readily imitate the abnormal song of their isolated colony founder, as will their offspring. But with each generation, the songs become slightly more similar to the typical species ‘format’, and within four generations a culture of wild-type songs will emerge de novo. This is because birds have an innate sense of aesthetics: while imitating a song, the bird modifies it a little to make it sound ‘right’.