This is a gorgeous violin/cello/bass instrumental cover of OneRepublic’s famous 2013 song Counting Stars. It’s included as the ninth track on Simply Three’s 2015 album Volume 2. It has no vocals, but the music speaks for itself – literally. :)
OneRepublic themselves have acknowledged the creation in a Tweet

I have to add that the Simply Three current violinist, Glen McDaniel, did not participate in this work. Instead a lady violinist contributed her talents, as shown in the music video.