Mitchell was a powerful force on the Hendrix band’s 1967 debut album Are You Experienced? as well as the trio’s albums Electric Ladyland and Axis: Bold As Love. He had an explosive drumming style that can be heard in hard-charging songs such as “Fire” and “Manic Depression.”

The Englishman had been drumming for the Experience Hendrix Tour, which performed Friday in Portland. It was the last stop on the West Coast part of the tour.

Hendrix died in 1970. Bass player Noel Redding died in 2003.

An employee at Portland’s Benson Hotel called police after discovering Mitchell’s body.

Erin Patrick, a deputy medical examiner, said Mitchell apparently died of natural causes. An autopsy was planned.

“He was a wonderful man, a brilliant musician and a true friend,” said Janie Hendrix, chief executive of the Experience Hendrix Tour and Jimi Hendrix’ stepsister. “His role in shaping the sound of the Jimi Hendrix Experience cannot be underestimated.”

Bob Merlis, a spokesman for the tour, said Mitchell had stayed in Portland for a four-day vacation and planned to leave Wednesday.

“It was a devastating surprise,” Merlis said. “Nobody drummed like he did.”

He said he saw Mitchell perform two weeks ago in Los Angeles, and the drummer appeared to be healthy and upbeat.

Merlis said the tour was designed to bring together veteran musicians who had known Hendrix – like Mitchell – and younger artists, such as Grammy-nominated winner Jonny Lang, who have been influenced by him.

Mitchell was a one-of-a-kind drummer whose “jazz-tinged” style was influenced by Max Roach and Elvin Jones, Merlis said. The work was a vital part of both the Jimi Hendrix Experience in the 1960s and the Experience Hendrix Tour that ended last week, he said.

“If Jimi Hendrix were still alive,” Merlis said, “he would have acknowledged that.”

During his career Mitchell played with the best in the business – not just Hendrix, but also Eric Clapton, John Lennon, The Rolling Stones, Jack Bruce, Jeff Beck, Muddy Waters and others.

Mitchell was a member of a later version of the Jimi Hendrix Experience that performed the closing set of the Woodstock Festival in August 1969 – where Hendrix played a psychedelic version of “The Star-Spangled Banner” before the band launched into “Purple Haze.”

The Jimi Hendrix Experience was inducted into the Rock Hall of Fame in 1992. According to the Hall of Fame, Mitchell was born July 9, 1947, in Ealing, England.

Hendrix, Redding and Mitchell held their first rehearsal in October 1966, according to the Hall of Fame’s Web site.

In an interview last month with the Boston Herald, Mitchell said he met Hendrix “in this sleazy little club.”

“We did some Chuck Berry and took it from there,” Mitchell told the newspaper. “I suppose it worked.”