The rock world mourned today as Malcolm Young, co-founder and guitarist for AC/DC and writer on a miles-long list of soundtracks for TV and film, died at age 64. He had been suffering from dementia and was no longer touring with the Australian hard rock band.

The band announced his death on its web site.

“Today it is with deep heartfelt sadness that AC/DC has to announce the passing of Malcolm Young,” the statement read. “He leaves behind an enormous legacy that will live on forever. Malcolm, job well done.”

Young was the rhythm guitarist and co-writer on all of the band’s music, which became a TV and film soundtracks staple for its anthemic choruses. His music graced such TV shows as The Sopranos and ER, and also enhanced films like Iron Man and The Avengers.

Another statement from the band noted that he died surrounded by family.

“Renowned for his musical prowess, Malcolm was a songwriter, guitarist, performer, producer and visionary who inspired many,” the statement read. “From the outset, he knew what he wanted to achieve and, along with his younger brother, took to the world stage giving their all at every show. Nothing less would do for their fans.”

Brother Angus Young said Malcolm’s legacy “will live on forever,” noting that he was stubborn, but “he stuck to his guns and he did and said exactly what he wanted.”

Reactions among the world’s top rockers and entertainers lit up Twitter.

Young was born in Glasgow, Scotland, on Jan. 6, 1953, and formed AC/DC with brother Angus in Sydney, Australia in 1973. The band’s debut album, High Voltage, arrived in 1975, starting a decades-long run as one of the world’s top hard rock bands.

The Young Brothers were credited as co-writers on every song recorded by AC/DC. Their stadium-sized, anthemic rock included a number of classics that have been featured in many TV shows and on film soundtracks, including You Shook Me All Night Long, Back in Black and Highway to Hell, among them.

AC/DC’s 1981 album, For Those About To Rock We Salute You, was their first to reach number one in the United States, no easy feat for an Australian band.