DAVID KERNS Ken Tesler is a Napa entertainment producer with several balls in the air. Arriving from the East Coast to open Blue Note in the Napa Valley Opera House in the fall of 2016, he went on to establish the Oxbow RiverStage concert series in 2019, and this year Blue Note at the Charles Krug Winery in St. Helena. At his Opera House office last week, Tesler talked about the challenge of the Covid pandemic. âI want to make sure I put things in context,â he said. âThe most difficult thing was what happened to a lot of people. We're extremely lucky that it didn't happen to us.