Musician Lou Reed, most known for his role as vocalist and guitarist of the influential rock band The Velvet Underground, died today at the age of 71. Rolling Stone reports that while the cause of death is currently unknown, Reed did undergo a liver transplant in May.

Besides serving as the leader of The Velvet Underground, Reed was also known for his productive career as a solo musician. His music often pushed the envelope of what constituted rock music, and often drew the ire of critics and the public for his racy lyrics and unconventional songwriting. The debut self-titled Velvet Underground album was initially panned by music writers when it was released in 1967, but soon became known as a landmark for rock music. Reed continued his career with a string of variable successful solo albums, and more recently collaborated with modern acts like Gorillaz and Metallica.