What’s your favourite love song?

“Unchained Melody” by the Righteous Brothers?

“Love will keep us together” by the Captain and Tennille? (It didn’t.)

Perhaps it is “I just want to be your everything!” by Andy Gibb, or “Everything I do, I do it for you” by Bryan Adams.

Impossible to choose.

Many couples have a special song, meaningful for a significant event in their lives – perhaps the day they met, or their wedding day, or simply one they loved to dance to. A song can trigger beautiful memories of pivotal moments in their relationship.

Most young men, however, do not sing to available and attractive girls in order to win a lifelong partner, or to cement a commitment. Nor do most young women sing to prospective boyfriends.

Gibbons, a small form of ape living in tropical jungles in south-east Asia, do just that. The male has a certain song which he hopes will attract a bride. The female likewise has hers. The dominant female’s song is referred to as a “great call” which is a series of loud notes accelerating in tempo and pitch. Her series of vocalisations tends to be essentially unchanged during her song, whereas the male starts with simple notes and then builds up the complexity. The fully developed form is reached only after several minutes.

If their songs are pleasing to each other, the gibbons will be drawn together – and form a life-long bonded and committed partnership, for gibbons are monogamous.

Even better, and more amazing, is the fact that once they are together, their songs blend, and they create a new song, their own special duet, unique for each couple. This duet, a series of coordinated vocal cries combining their individual mating calls into a single song, becomes intrinsic for their relationship. It's their own unique love song.

Both partners contribute to their special piece, and they have interludes and alternating sequences of singing which are characteristic of their gender and of their species. Researchers can thus locate particular species of interest by their style of singing.

Their duets are complex, and for specific times of the day, particularly early morning. They also sing their songs of love while they groom each other, and during moments of intimacy.

Their song proclaims their territorial rights, as well as their attraction, and their commitment to the maintenance of their bond. The female tends to mostly remain in the middle of their territory, but she keeps her song going when they are separated so that the male never wanders beyond earshot of their love song and their “home”.

How very beautiful.