Last summer, I spent a month in Salzburg, Austria, and I eschewed Mozart tourism the entire time. Some things are unavoidable — the Mozartkugeln chocolates in every supermarket, the opera festival founded in his memory — but I wanted to appear as a local, and guided tours don’t give that impression. Now I see it was a missed opportunity. Lucky for me, and all of New York City, a second chance presents itself at the Morgan Library. Wolfgang Amade…