I’m sad that I’m going to miss this concert – the season opener for the Portland Youth Philharmonic – at the Arlene Schnitzer Concert Hall Saturday night. For one thing, it’s an all-American concert – a relative rarity in concert halls these days. In addition, it’s an opportunity to hear OSO concertmaster Jun Iwasaki as soloist in the Leonard Bernstein’s Serenade for Violin, Harp, Percussion and Strings – another piece that’s not programmed as often as it should be. Finally, most of us know Howard Hansen’s Second Symphony, but I’ve never heard his Third Symphony (which would make a great third leg of a concert stool with the Third Symphonies of Roy Harris and William Schuman). And speaking of Schuman, the concert opens with his orchestration of Charles Ives’ Variations on America, a great showpiece for the full orchestra.