When evolution hits on a solution that works, that solution tends to get reused. Researchers have found that genes that play key roles in development typically get deployed over and over again in different tissues. Once this happens, however, it can create a problem: you can’t make major changes to the gene without messing up a whole lot of essential processes.

This week, however, a team of researchers from the Janelia Research Campus describe a case in which an essential gene that’s critical for neural activity was tweaked in an incredibly subtle and specific way. The new version of the gene changed only a single feature of the species it evolved in: the details of the male courtship song.

You might not think fruit flies would do much in the way of singing, and they don’t in the traditional sense. But their courtship behavior involves a song created by rapid vibrations of their wings. The song is a mixture of repeated chirps interspersed with longer, buzzing vibrations. The details of this song—the frequency of the buzzing, the space between the chirps, etc.—often varies among the dozens of species of Drosophila we’ve identified.