Mike Pinder, the last surviving founding member of the Moody Blues, whose innovative use of the Mellotron — a predecessor of the sampler — helped make the band a pioneer of progressive rock, died on Wednesday at his home in the Sacramento area. He was 82.

His son Dan confirmed the death. He said that his father had breathing difficulties and had been in hospice care for a few days.

The Moody Blues were formed in 1964, with a lineup of Mr. Pinder on keyboards, Denny Laine on guitar, Graeme Edge on drums, Ray Thomas on flute and Clint Warwick on bass. The group’s “Go Now!,” sung by Mr. Laine, rose to No. 10 on the Billboard Hot 100.

Mr. Laine and Mr. Warwick left after the release of the band’s first album, “The Magnificent Moodies” (1965), and were replaced by Justin Hayward and John Lodge. The change in personnel set the stage for a change in direction: from R&B-tinged rock to the psychedelic, orchestral sound that the Moody Blues vividly showcased on their breakthrough 1967 album, “Days of Future Passed.”

Mr. Pinder had worked as a tester in the Mellotron factory in Birmingham, England, before the Moody Blues formed. Playing the company’s Mark II model for the first time was “my first ‘man on the moon’ event,” he told the British music website Brumbeat.