Music producer Hal Willner, one of the creative forces behind Metallica and Lou Reed's collaborative 2011 album, Lulu, died Tuesday (April 7) due to complications of the novel coronavirus (COVID-19). He was 64.

In response, Metallica — who admitted they were "shocked and saddened" by the death — shared a statement saluting the musical icon. It arrived alongside a behind-the-scenes photo of the band working with Willner and Reed in the studio. See it down toward the bottom of this post.

Willner was best known as a Saturday Night Live sketch music producer and a curator of tribute albums and historical music revues in a wide variety of styles. He first alluded to his COVID-19 diagnosis in a March 28 tweet, as Variety pointed out. Later that month, he mentioned the coronavirus-related difficulties facing country icon John Prine, who himself succumbed to complications the same day that Willner died.

Metallica were "shocked and saddened to hear of producer, writer, and composer Hal Willner's passing earlier today," the group shared Tuesday. "He was a truly inspirational collaborator, someone who through his unique combination of musical knowledge and warm personality, invigorated every project he touched."

Metallica drummer Lars Ulrich added, "I will always treasure the time I spent with Hal in those most inspiring and collaborative environments. He was such a warm, open and communicative person, and as Lou's right-hand man, he was absolutely essential in pushing Lulu forward. I'll never forget him."

In the lineage of Metallica projects, Willner indeed secured his place in the rockers' pantheon with his co-producer contributions to Lulu, the outré double album from the two marquee artists that remains a polarizing entry among metal fans. Reed died of liver disease two years after it was released.

But Willner's place in the larger musical world was anchored by the many tribute and variety albums he helmed. Lost in the Stars: The Music of Kurt Weill (1985), Stay Awake: Various Interpretations of Music from Vintage Disney Films (1988), and Rogue's Gallery: Pirate Ballads, Sea Songs, and Chanteys (2006) are just a few.