Donald "Duck" Dunn of the legendary group Booker T. and the MGs died at 70 years old Sunday.

News of Dunn's death was delivered by his family. The bassist died in his sleep in Tokyo while on tour, his son told CNN.

"They were over there doing five shows in a row, two shows every night- and for a 70-year-old guy, that was quite a bit of work," Jeff Dunn explained. "

Dunn returned to his hotel after their last show, and just hours before he was scheduled to return to the U.S., he died.

Dunn was touring in Japan with fellow Stax veterans including Steve Cropper, who was a high school classmate and who also played with Booker T. and the MGs.

"Today I lost my best friend," said Cropper in a statement on his website Sunday. "The world has lost the best guy and bass player to ever live."

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The group's leader, Booker T., also mourned Dunn in a statement on his website.

"It was totally unexpected," said the singer. "And I've rarely had tears come so quickly."

Booker T. and the MGs was part of Memphis, Tennessee's Stax Records and is well known for their hits such as "In the Midnight Hour" and "Sitting on the Dock of the Bay," for which Dunn contributed his guitar skills.

The bassist's work included sessions with music legends such as Levon Helm, Eric Clapton, Neil Young, and Bob Dylan.

He was also a member of the Blues Brothers, the band that backed comedians John Belushi and Dan Aykroyd during "Saturday Night Live" appearances and filming.

"Duck Dunn was the backbone of the Stax/Volt era," said Aykroyd in a written statement. "He was and will remain universally loved by all that knew him. His talent, knowledge and warmth, and especially his humor will be greatly missed."

On Twitter, fans are expressing their condolences and respects to the late bassist.

"Sorry to hear about the passing of Donald Duck Dunn, Blues Brother and one of the greatest R&B bass players of all time," wrote Chris.

The Rolling Stones magazine posted, "RIP Donald 'Duck' Dunn, inspirational and incredibly gifted bass player. Condolence to all who loved him."

"RIP Donald 'Duck' Dunn," posted the rock band Nickelback. "You inspired countless people with your gift of music. Heartfelt condolences to your family, friends, and fans."

Singer Rob Thomas wrote on Twitter: "R.I.P. Donald 'Duck' Dunn."

Dunn and the Booker T. and MGs were inducted into the Rock and Roll Hall of Fame in 1992, and in 2007 the bassist received a lifetime achievement Grammy Award.

The causes of his death are unknown, according to Dunn's son. A memorial service for the bass player will take place in Memphis at a date to be announced.