DOWNTOWN DELIGHTS The River to River Festival offers more than 500 free events in Lower Manhattan. Today’s opening celebration is an “Un-Parade,” led by seven trombones and a grand marshal, which proceeds to Pier 17 from Battery Park City with stops at a variety of downtown art installations and musical moments (today, noon-2 p.m., meet at Battery Park City’s Oval Lawn). Later in the day, Tan Dun conducts a performance of his full-length choral composition “Water Passion After St. Matthew,” written for voice, percussion, violin, cello, and 17 water bowls (tonight, 8 p.m., South Street Seaport, Pier 17). Upcoming highlights include a performance by Audra McDonald that pays tribute to the “Swedish nightingale,” Jenny Lind (Friday, 5 p.m. tickets distributed, Castle Clinton, Battery Place at Hudson River). Festival: Today through Saturday, September 17, various locations, 212-835-2789, free. Please see www.rivertorivernyc.com for a full schedule.

COMPUTER AGE The elder statesmen of electronica, Kraftwerk, have been making music with computers since the 1960s. The techno-savvy duo performs tonight in Manhattan. Tonight, 6:30 p.m. doors open, Hammerstein Ballroom, 311 W. 34th St., between Eighth and Ninth avenues, 212-777-1224, $45.

REACHING NEW AUDIENCES A concert that’s part of the About the Audience series presents new compositions for flute, violin, and piano. The series intends to attract new audiences to classical music by producing concerts organized by theme or instrument. Audience members are also invited to give feedback to the composers. Tomorrow, 8 p.m., CAMI Hall, 167 W. 57th St., between Sixth and Seventh avenues, 917-204-4922, $21.

To submit an event for consideration for the Calendar, please wire the particulars to calendar@nysun.com, placing the date of the event in the subject line.