This week I’m going to be covering the Tune-In Festival at the Park Avenue Armory for Musical America. Earlier this month, the Armory made the news for another high profile arts endeavor. It was announced as the site for the New York Philharmonic’s performance of Karlheinz Stockhausen’s Gruppen during the 2011-’12 season. Just as the venue’s large Drill Hall is ideal for a work such Gruppen – a spatial music extravaganza for three orchestras – it’s also ideal for a number of works on the Tune-In Festival that are conceived for unconventional venues. Tonight is the premiere of Arco, a