Mr. Sack, who lived in Merion, died Sunday of acute myelogenous leukemia at the Hospital of the University of Pennsylvania. He was diagnosed with the disease last Labor Day weekend. Yesterday, a statement on the Web site of the band - whose members include Zach Djanikian, Matt Kass, Derek Feinberg, and Adam Flicker - said that, since his diagnosis, "Josh bravely fought the cancer, even regaining his strength long enough to tour in October and drum at rehearsals as recently as last week."

He endured grueling chemotherapy sessions, a bone-marrow transplant from his brother, William, and total body radiation, and he was about to try another transplant and more radiation, said his mother, Joan Kellmer Sack.

A graduate of Lower Merion High School, Mr. Sack played piano, upright bass and guitar as well as drums. He studied drums at Berklee College of Music in Boston for a year but left school to tour with The Brakes. "He was so excited," his mother said. "We decided college would still be there."

Mr. Sack and his band performed at the South by Southwest Music Festival in Austin, Texas, in 2006 and at the Xponential Music Festival in Wiggins Park in Camden last summer. The group released three self-titled EPs in 2004, 2005 and 2006, and its song "Special" was featured in an H&R Block TV commercial in 2006.

Legendary producer Joel Dorn, who died in December, served as a mentor to the band, and traveled from New York to see it perform at Milkboy Coffeehouse in Ardmore. A Tale of Two Cities, which is to be released on the Hyena label, was recorded there, and at the Knitting Factory in New York. The band will begin a U.S. tour Saturday in Dallas with substitute drummer Spencer Cohen.

Mr. Sack told his parents he wanted to learn to play the drums when he was 8. "We thought it was a passing fancy," his mother said. Instead he became a drum prodigy. "He just blossomed," she said. He liked a broad spectrum of music including pop and rock and played drums in the jazz band at Lower Merion High School.

In addition to his mother and brother, Mr. Sack is survived by his father, David H. Sack; and grandmothers Marjorie Kelmer and Esther Sack.

A memorial service will be at 11:30 a.m. today at Joseph Levine & Son Memorial Chapel, 2811 West Chester Pike, Broomall. Memorial donations may be sent to the Leukemia and Lymphoma Society, Box 4072, Pittsfield, Mass. 01202 or www.leukemia-lymphoma.org. Condolences, memories or messages to the band can be sent to management@brakesband.com.