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.

So he understood the musical possibilities of using the Mellotron, an electromechanical keyboard that uses tape loops to simulate the sounds and rhythms of an orchestra, on “Days of Future Passed” and beyond.

“With the ’Tron, I could develop melodies and countermelodies within the Moody Blues’ songs,” Mr. Pinder told Rolling Stone in 2018 for its oral history of “Nights in White Satin,” the album’s signature song, which was written and sung by Mr. Hayward. “When you become the orchestra, I think you become the arranger by default. I could create the backdrops and the landscape for the melodies that the guys were writing.”

After Mr. Pinder’s death, Mr. Hayward wrote on Facebook: “Mike was a natural born musician who could play any style of music with warmth and love. His reimagining and rebuilding (literally) of the Mellotron gave us our identifiable early sound.”

Mr. Pinder said that he had recommended the Mellotron to John Lennon. It was played by Paul McCartney on the Beatles’ 1967 single “Strawberry Fields Forever.”

“Days of Future Passed” also featured Mr. Pinder’s baritone-voiced recitation of “Late Lament,” the mystical coda (written by Mr. Edge) to “Nights in White Satin.” Mr. Pinder was lying down “in a meditative state,” he said in the oral history, when he recited the poem that famously begins, “Breathe deep the gathering gloom/Watch lights fade from every room.”

Michael Thomas Pinder was born on Dec. 27, 1941, in Erdington, a suburb of Birmingham, and grew up in nearby Kingstanding. His father, Bertram, was a bus driver, and his mother, Gladys (Lay) Pinder, was a barmaid.

Michael had no formal training and started playing the piano and guitar when he was young. He was in the British Army, where he performed with a band, when he first heard the Beatles.

“When I heard ‘Love Me Do,’ it was like, ‘OK, that’s what I’ve been waiting for,’” he told the website Classic Bands in an undated interview. “I’ve been waiting for that signal, because the music scene in England up until then was pretty poor.”

When they formed in 1964, the Moody Blues were called the M&B 5, using the initials of the brewery that owned clubs and dance halls where they had been playing. The name was a ploy to get money from the brewery to fund the band. It didn’t work. So, Mr. Pinder told Classic Bands, he was inspired to create the name Moody Blues by tying together “the mood affecting changes of music” and the fact that the band’s repertoire at the time was primarily rhythm and blues.

Mr. Pinder remained with the Moody Blues until 1978, providing vocals and contributing songs as well as continuing to use the Mellotron on albums like “In Search of the Lost Chord” (1968) and “On the Threshold of a Dream” (1969). He moved to another electromechanical keyboard, the Chamberlin, for “Seventh Sojourn” (1972), and the synthesizer for “Octave” (1978).

By then, he had already released a solo album, “The Promise,” in 1976. He spent many years off the scene, part of that time consulting on composing music for computers for Atari, the video game maker, before recording a second album, “Among the Stars,” in 1995. He also recorded two albums for children, “Planet With One Mind” (1995) and “A People With One Heart” (1996), in which he told stories, accompanied by his musical arrangements.

“We wanted stories that had multilevel meanings,” he told The San Francisco Examiner in 1997, referring to the search for the right picture books that he pursued with his wife, Taralee (Grant) Pinder. “We went through hundreds of books. We were looking through a lot of books that were like, ‘The rabbit went down to the mouse’s house for a cup of tea.’ But we were looking for books like, ‘The rabbit went down to the mouse’s house and discussed the Zen of tea making.’”

In addition to his wife and his son Daniel, from his marriage to Donna Arkoff, which ended in divorce, Mr. Pinder is survived by two other sons, Michael and Matthew, from his second marriage; four grandchildren; and a sister, Monica Hackett.

After the Moody Blues were inducted into the Rock & Roll Hall of Fame in 2018 — nearly 30 years after they first became eligible — Mr. Pinder wrote about the ceremony on his website.

“All the band brought their children and grandchildren and that was magic,” he wrote. He added: “Many MB fans have asked why I did not speak at the induction, but by the time the Moodies took the stage, we were five hours into the ceremony. The oldest of the inductees were up the latest.”