Soul rockers Booker T and the MGs seen in 1970 photo: Al Jackson Jr., left, Booker T. Jones; Donald "Duck" Dunn; and Steve Cropper. Bass player and songwriter Dunn died iMay 13, 2012. He was 70. (Anonymous/AP)

Donald “Duck” Dunn, the bass guitarist whose bouncy rhythms helped define the Memphis soul sound of Stax Records and graced recordings by Otis Redding, Wilson Pickett, the Blues Brothers, Booker T. and the MGs, Eric Clapton and Rod Stewart, died May 13 in Tokyo. He was 70.

His longtime collaborator, guitarist Steve Cropper, announced Mr. Dunn’s death online but did not specify a cause. Mr. Dunn and Cropper had been performing at a Tokyo nightclub in a revue of Stax performers.

Mr. Dunn played on such classic soul hits as Pickett’s “In the Midnight Hour” (1965), Eddie Floyd’s “Knock on Wood” (1966), Sam and Dave’s “Soul Man” (1967) and Redding’s “Sittin’ On the Dock of the Bay” (1968) — all from the Stax studio where Mr. Dunn was in the house band, Booker T. and the MGs. Stax, with its bluesy, gritty sound and spontaneous approach to recording, rivaled Motown in popularity among soul fans.

Booker T. and the MGs (or MG’s as they were later billed) — Mr. Dunn, Cropper, drummer Al Jackson Jr. and organist Booker T. Jones — also crafted such memorable instrumentals as “Time is Tight” (1969) and the Latin-flavored “Soul Limbo” (1968). The name MGs reportedly stood for “Memphis Group.” Jones had earlier played in a band named the Triumphs — a fact that helped lead many people to believe that the band was named after the English sports car, the MG.

As a studio band, the MGs made infrequent concert appearances. However, they toured Europe as part of a Stax revue in 1967. That year, they also backed Redding at the Monterey International Pop Music Festival, where Mr. Dunn recalled that their mohair suits stood out from the more prevalent psychedelic fashions.

Unlike many other soul bands of the era, the MGs were racially integrated. Despite the prevailing racism, Stax did not seek to conceal that fact on the group’s album covers.

Mr. Dunn and Cropper knew each other from high school and earlier bands — they had been in the original lineup of the Mar-Keys, the brass-dominated group that gave Stax its first hit, “Last Night” in 1961 — and were white. Jones and Jackson were African-American. Mr. Dunn joined the group in 1963, replacing original bassist Lewis Steinberg.

Onstage, Mr. Dunn seemed to conduct the band as he moved in time with the music and signaled the shifts in a song’s rhythm. Although he at times played busily, Mr. Dunn generally ascribed to the “less is more” theory of music — an approach he attributed to his long history with Jackson.

“Al would say, ‘Dundedunn, wait on two and then play,’ ” Mr. Dunn once said, according to his Web site. “A lot of players know all the notes, but can’t get a feel for the music, and that’s what he was talking about.”

Mr. Dunn also recalled Jackson’s advice to simplify a song’s meter. “If you play in sixteenths, think eighths; eighths, think quarters,” Jackson told him. “The thoughts will be simpler, and it won’t be as busy. And always smile.’ ”

The MGs disbanded in the early 1970s when Jones embarked on a solo career. Mr. Dunn continued to work for Stax as a bassist and producer until the label’s demise in the mid-1970s. His later credits included work with Levon Helm, who died recently, John Fogerty and Crosby, Stills, Nash & Young.

Perhaps the most conspicuous of his later performances was with the Blues Brothers band, where he and Cropper accompanied comedians Dan Aykroyd and John Belushi. Mr. Dunn appeared in the spinoff movie “The Blues Brothers” (1980) and a sequel, “Blues Brothers 2000” (1998), in which John Goodman replaced Belushi.

Booker T. and the MGs reunited several times in later decades without Jackson, who was murdered in 1975. The group accompanied Bob Dylan at Madison Square Garden in 1992 and the next year toured behind Neil Young. They were inducted into the Rock and Roll Hall of Fame in 1992 and received a lifetime achievement Grammy award in 2007.

Donald Dunn was born Nov. 24, 1941, in Memphis. His father, a candymaker, nicknamed him Duck after the Disney cartoon character. In high school, he and Cropper started a rhythm-and-blues band, the Royal Spades.

Survivors include his wife, June; a son, Jeff; and a grandson.

Mr. Dunn often joked that he took up the four-stringed bass guitar because the standard six string had “two strings too many,” as he put it, according to his Web site. “It was just too complicated, man!”