In the Georgian-Estonian film Tangerines (2013) at the end of the film as it rolls into the credits what is the song that is being played? It sounds like a rock/alternative song. What was the context and significance of the song?
So after finding some English translations of the song it has become quite clear of the significance of the song.
From my understanding the gist of the song is about coming home to a loved one and the fact that the person singing can't stop thinking about them. “I will swim over the sea, Don’t listen to anybody else saying I won’t come, I will come back to you, I will return.” --So it no surprise Nika had a cassette with this song on it given he is in a war. Like DA said in the comments it was probably also put there for aesthetic purposes.
The song was popular among fighters back in the war in 1992, Irakli Charkviani’s Qavagadi Navi (A Paper Boat) – a promise to return no matter what.
I found a complete English translation of this song (and great interview with the director) which has been haunting me ever since I saw this film a few weeks ago:
I want to be with you again Even when I fight, I am with you in my dreams I´ll be back, I´ll sail back on a paper ship I´ll come back to you from over the seas Don´t believe it if they say I won´t come back I will come back to you
— Irakli Charkviani, “A Paper Boat,” 1992