It's better to start with example. (Sadly, it deleted from Youtube). 2014. Russian Federation just captured Crimea from Ukraine. To celebrate, they invited Cuba

It's better to start with example. (Sadly, it deleted from Youtube). 2014. Russian Federation just captured Crimea from Ukraine. To celebrate, they invited Cuban Cossack choir from RF. When choir started to sing, everyone started to laugh. Why? Because choir signs folk songs in their native, Ukrainian language. If you dig deeper, you will see that every folk choir in Russia has it repertoire split in two parts: songs in Russian, and folk songs in their own native language. Yep, it's possible for folk songs to exist in Russian language. However, currently, no folk songs in Russian language are found. I spent years looking for one.