Flaco Jiménez, who has died aged 86, was a master accordion player who transformed the Tex-Mex music scene in the US. A virtuoso performer of tejano conjunto – a fusion of Mexican styles and the polkas of German immigrants to the south-western states – he updated the form by adding rock, blues or country influences. He said he wanted the accordion to “yell and scream, and make it happy”.

He worked as a soloist, with his own bands including the supergroup the Texas Tornados, which he co-founded, and with a remarkable range of musicians, including Ry Cooder, Bob Dylan and the Rolling Stones. His many accolades included five Grammys, one of which was a lifetime achievement award in 2015.

Jiménez’s 70-year career started out in the dance halls and bars of his hometown, San Antonio, Texas, and along the Mexican border. He became a regional celebrity but grew bored with “playing the same way for years”. Doug Sahm, a fellow Texan and the adventurous former leader of the country-rock band Sir Douglas Quintet, changed all that when he began working with Jiménez and invited him to play on his 1973 album Doug Sahm and Band – joining a celebrity cast that included Dylan and the New Orleans pianist Dr John. The album begins, suitably enough, with the upbeat (Is Anybody Goin’ to) San Antone and includes a rousing Jiménez accordion solo on Poison Love.

Then came Cooder, who invited Jiménez to play on his gloriously inventive 1976 album Chicken Skin Music. “He tracked me down,” Jiménez said. “I had never heard of him but he opened my eyes.” He toured the UK with Cooder and his band, and recorded a memorable concert with them for the BBC’s Old Grey Whistle Test in 1977 that included accordion-backed reworkings of the folk song Goodnight Irene and the Jim Reeves country classic He’ll Have to Go. The musical partnership would continue for decades. Jiménez’s many recordings with Cooder included Get Rhythm (1987) and Pull Up Some Dust and Sit Down (2011).

Helped by the collaborations, Jiménez’s solo career flourished. His first solo album was released in 1972 on the San Antonio DLB label; more than 25 would follow, including several for Arhoolie Records, run by Chris Strachwitz, famed for promoting American roots styles. Jiménez’s 1985 recording Ay te Dejo en San Antonio, made with the singer Toby Torres, won Arhoolie a Grammy.

During the 1980s he also toured with the bluegrass star Peter Rowan, with whom he recorded the witty and defiant ballad The Free Mexican Airforce (from the album of the same title), and played on the country stars Dwight Yoakam and Buck Owens’s single Streets of Bakersfield, taken from Yoakam’s 1988 album Buenas Noches From a Lonely Room. Rowan later appeared, along with Cooder, on Jiménez’s album Flaco’s Amigos (1989).

In the same year he was reunited with Sahm, along with Augie Meyers and Freddy Fender, in the Texas Tornados, who won a Grammy for the song Soy de San Luis, written by Jiménez’s father, which appeared on their debut album. A popular touring band, they went on to release half a dozen more albums, including two live sets.

In 1990 he was reunited with Dylan, whom he joined at the Montreux jazz festival to perform Across the Borderline, co-written by Cooder. He returned to the song (this time with vocals from John Hiatt) on his 1992 album Partners, which also included contributions from Stephen Stills, Cooder and Linda Ronstadt. The album was selected for the US Library of Congress Recording Registry for recordings deemed “of special historical significance”.

His least expected collaboration came in 1994, when he was on tour in San Francisco and was invited to record with the Rolling Stones. He went to the studio, played along with the song Sweethearts Together, then said he was ready to record – only to be told by Mick Jagger that they had already recorded what he was doing. The result can be heard on the Voodoo Lounge album.

In 1995 he played on the Mavericks hit All You Ever Do Is Bring Me Down, and in 1998 won another Grammy with another supergroup, Los Super Seven, in which he was joined once again by Sahm and Fender, along with Joe Ely and members of Los Lobos. In 2000 he teamed up with Sahm yet again, this time on his own album Sleepytown, which also included Yoakam and Owens.

Born Leonardo Jiménez in San Antonio, he was known since childhood as Flaco (Spanish for skinny). He was the son of Santiago Jiménez, a successful accordion player, and his wife, Luisa (known as Mena), who ran a home filled with music. His grandfather, Patricio, had played conjunto, as did his father, who recorded several regional hits. Flaco started out playing bajo sexto guitar, a 12-stringed Mexican instrument, then switched to the accordion when he was seven. At 15 he started a band, Los Caporales, and began playing on local radio stations at the start of a career that would transform Texan music.

He slowed down in his later years, but continued to mix recording and performing. In 2020 he was reunited with the Mavericks on their first all-Spanish album, En Español, and in May 2024 he gave his last performance at the annual Tejanto Conjunto festival in San Antonio.

He is survived by his wife, Adela, whom he married in 1969 and with whom he once ran a food truck, Taco Jiménez, by their children, Raquel, Rebecca, Cynthia, Gilbert, David, Leonardo, Arturo and Norma, and his brother, Santiago Jr, another celebrated accordion player.

• Flaco (Leonardo) Jiménez, musician, born 11 March 1939; died 31 July 2025