The Swedish YouTube duo of Philip Tillström and Nicolai Kjellberg are known as Hearts & Colors, and their voices blend so beautifully, they put me in mind of Simon & Garfunkel. They’re that in synch. Even their man buns match!
No original music from them yet, but their covers are lush and lovely and eminently listenable. Both their YouTube channel and their Sound Cloud have mostly 1-2-minute versions of the songs they cover (I assume for copyright reasons), and their Facebook feed has some 1-minute quickies which are definitely worth a listen. It even includes a couple of live videos of them busking! If you want to get the full-length versions of their songs, they’re available on Spotify.