All animals, even some humans, have a mating call to call upon a faithful mate. Some birds have a very unique song they sing with the occasional puff up off the chest, while others sing duets.
Scientists have found that lar gibbons sing rhythmic duets in time with each other to set up social bonds. These melodious call-and-reaction songs are comparable to human music. In addition, they discovered that this is mainly present among ladies and men at some stage in courtship.
“Male and female lar gibbons sing duets with notes that are synchronised and occur at regular intervals. These are rhythmic qualities similar to those found in human songs, which could hint at an evolutionary basis for the origins of music.”