The performance lineup, along with other details of the three-day festival that attracts about 350,000 visitors each year, was announced Wednesday by Mayor Stephanie Rawlings-Blake.
McKnight, a 16-time Grammy nominee whose albums have sold millions of copies, will perform at 7:30 p.m. July 20.
Clutch, whose four members hail from Germantown, has released nine albums, most recently 2009's "Strange Cousins from the West." The band will play at 7:30 p.m. July 21.
The Rebirth Brass Band won a Grammy this year for the album "Rebirth of New Orleans" and will close out Artscape 2012 with a performance at 6:30 p.m. July 22.
Seating will be on a first-come, first-served basis. No tickets are required.
Other acts scheduled during the nation's largest free arts festival, set for the area surrounding
Two other stages will also feature live music. Performers on the Festival Stage, set up on Mount Royal Avenue near Mosher Street, include bluesman Tom Principato, Irish rockers Donegal X-Press, country singer Juliene Irwin, the jazz-R&B band Café Red and soul/hip-hop artist Maimouna Youssef.
Other new features of Artscape 2012 include Roadside Attraction, a quarter-mile stretch of Charles Street to be festooned with sculpture, performances, live music, art cars and more; At-TENT-ion, an art installation composed of 20 tents designed by different artists; and Face Forward, a 16-foot human face designed by artist Christian Ristow, where visitors can manipulate the muscles and create expressions.
Artscape runs 11 a.m. to 9 p.m. July 20 and 21 and 11 a.m. to 8 p.m. July 22.