Malcolm Young, the guitarist and songwriter who helped found the Australian rock band AC/DC, died on Saturday. He was 64.

His family confirmed the death in a statement, adding that Mr. Young had had dementia for several years. It did not say where he died.

Mr. Young and his brother Angus created AC/DC and played their debut show at a Sydney, Australia, club on New Year’s Eve in 1973.

The group, known for its power-chord riffs, earsplitting vocals and raucous energy, found enduring popularity and great commercial success despite waiting until 2012 to release its music catalog to iTunes.