It's a puzzle ! I was looking for another video when I saw the image of an old postcard of the iconostasis of Rocor-MP's Holy Virgin Cathedral in San Francisco. I recognized that right away - because exactly this postcard fell on the floor in front of me yesterday. It's easy to see anyway due to the faded color tone and the earlier arrangement of Icons. In this old postcard, the life size -- Angel size -- Archangel Michael icon is still standing on the far left front of the picture. This magnificent work was done by the émigré icon painter from Harbin, China, Nikolai Zadorozhny. Whereas after Rocor's 2007 union with the Moscow Patriarchate, this masterpiece was unfortunately relegated to the back corner on the same side of the Church and replaced by something else.
Seeing the title of the video was "Optina Pustyn Men's Choir", I clicked on it to see what the connection might be.
It's still a mystery, as there is no mention in the notes. I don't believe there was ever a concert by this choir conducted there. Maybe someone at Optina liked the frescoed interior of the Cathedral where the relics of St John Maximovitch lie ?