D.C.’s convention season runs year-round, which means there’s no end to the hordes of disoriented suits in nametags who swarm Woodley Park, searching for Chipotle. No one wants to help them because, really, what do they do for us besides take up both sides of the escalator? This weekend though, Metro riders should be less hostile to the Nordöstlicher Sängerbund (Northeastern Singers’ Federation) of America, which will convene here for its 50th triennial Sängerfest, kind of like Oktoberfest but with more singing. Because, unlike the National Association of Realtors, the Germans have a gift to share with us. Their Saturday concert will fill the National Building Museum with some 300 vocalists accompanied by the National Gallery Orchestra for a performance of Austrian and German operettas, as well as a number of American patriotic tunes that probably entered the U.S sängerbund repertoire by coercion during World War I. THE FEST CHORUS PERFORMS SATURDAY AT 5 P.M. AT THE NATIONAL BUILDING MUSEUM, 401 F ST. NW. $25. (703) 644-0565.