Many thanks to @scotttixier for tweeting the youtube link to the site!
Scott Tixier is a jazz violinist and composer based in New York. You can read more about him and listen to some of his work at his site.
He played in the band that appeared in John Wick. He posted an excerpt from the John Wick ‘Behind the Scenes’ video that contains footage of the Candy Shop Boys. You can view it here.