This is the Largo from the Lute Concerto in D major by Antonio Vivaldi. Note that I use the D major chord sometimes as a D minor chord by muting the F# note (1st left) with the thumb and borrowing an F natural from the F major chord (next chord to the right). I am using my 6-chord zither, a 100 years old German instrument. See details of the decorations in the video.