Fans of experimental pop music were saddened to learn that Robert Haimer had passed away this weekend at the age of 69. 

The Brooklyn Vegan reported that Haimer, who was also known as Artie Barnes, died on Saturday following "a long illness."

Bandmate called Haimer "a one of a kind artist and person"

The website also quoted a Facebook post put up by actor and musician Bill Mumy, who appeared alongside Haimer in their group Barnes and Barnes.

"I’m so sad to share the news that Robert Haimer, my friend since childhood and musical partner in Barnes & Barnes passed away this morning after a long illness," Mumy wrote.

Mumy praised Haimer for being "a one-of-a-kind artist and person," adding, "Our relationship was based on harmony as was our music."

"Sometimes there was dissonance and silence and sometimes we made a mighty raucous roar together. I will miss making that unique 'Barnes' music very much," he continued.

Haimer wrote single "Fish Heads"

Mumy recalled how Haimer "made many people happy with his talent and his humor." What's more, he credited Haimer with writing "Fish Heads," the band's biggest hit.

"As with a lot of our catalog, I just helped him fill in the blanks. I’m feeling stunned and somewhat shattered right now," Mumy wrote.

"My love to his wife Faithe, his sons Wynn and Ian, his brother Brian and all who knew and loved him. Robert’s music lives on. Enjoy it," Mumy concluded.

Other tributes to Haimer quickly appeared on social media, including from comedian Dan Pasternack, who praised the musician for being "wild, wondrous and wholly."

Haimer called "absolutely brilliant"

Sad news to share. The wild, wondrous and wholly unique Robert Haimer AKA "Artie Barnes" of Barnes & Barnes... the macabre musical duo responsible for the @drdemento hit song Fish Heads has passed away. RIP to my "Guardian Artie." I will miss him. pic.twitter.com/OdSeSNSXef

— Dan Pasternack (@DanPasternack) March 4, 2023

Meanwhile, the artist liaison for Needlejuice Records described Haimer as "an absolutely brilliant and truly one-of-a-kind artist."

She added that Haimer was "a very close friend" and "a mentor" who she is "grateful to have had the honor of knowing him and working with."

Yesterday morning the world lost Robert Haimer, an absolutely brilliant and truly one of a kind artist. He was a very close friend of mine and a mentor to me. I’m grateful to have had the honor of knowing him and working with him. I feel shattered. We love you, Robert pic.twitter.com/nVx2duoD88

— Kendra 🧀 (@mysticalshit69) March 5, 2023