NEW YORK - When the White House operator tracked down Senator Patrick Leahy two decades ago to take a call, the secretary of state, Warren Christopher, asked the lawmaker to "turn down the radio."

Copies of "Rocking The Cradle: Egypt 1978" by the Grateful Dead are shown at Best Buy on October 14, 2008 in New York City. The band are set to play what could be their last gig together over the July 4, 2015 weekend.

Leahy, however, explained that he was not at home but at a concert, where Sting was opening for the Grateful Dead.

The top US diplomat, Leahy recalled, asked the senator incredulously whether he had time to speak to the president or was preoccupied with rock 'n' roll.

"And, of course, it was Clinton. And he wanted to come join us," Leahy remembered with a laugh.

Both Bill Clinton and Leahy, who with 40 years in office is now the most senior member of the US Senate, are fans of the Grateful Dead, one of the iconic rock bands from the 1960s who announced Friday that the surviving members would play what could be their last concerts together on the July 4 weekend in Chicago.

"I think it's great; I'm delighted," Leahy said of the reunion for the band's 50th anniversary.

"The difference between a live concert and their recordings -- as good as their recordings are -- it's night and day. It becomes a happening that even somebody at my age can enjoy," the 74-year-old senator told AFP by telephone.

The Grateful Dead weaved the blues, folk and other genres into performances marked by heavy improvisation. While producing few hits in the traditional sense, the band cultivated a following of thousands of "Deadheads" who would follow the band and swap bootleg recordings.

The communal experience took on a nearly spiritual feel in the hippie era. Other Deadheads who later achieved prominence included former vice president Al Gore, his wife Tipper Gore and Apple cofounder Steve Jobs.

- 'A unique sound' -

As for why the Grateful Dead enjoys such influence, Leahy credited the band's then "radical" step of not only allowing but encouraging fans to make recordings. But mostly Leahy pointed to the band's musical skill and integration, with Dead members able to "play off each other."

"When you listen to it, you think, 'Wait a minute, that tone is wrong,'" he said. "Then you realize it all fits together. They had a unique sound."

The three reunion concerts will take place at Soldier Field, the oldest stadium in American football and the site of the Grateful Dead's last concert in July 1995 with founding frontman Jerry Garcia, who died a month later.

Three musicians will join the post-Garcia Grateful Dead in Chicago, including Phish singer and guitarist Trey Anastasio. The band -- from Leahy's state of Vermont -- have similarly developed a base of traveling fans.

"It's great because if there is any group in the country that sort of follows the Grateful Dead legacy, it's Phish," Leahy said.

Leahy said that both the Grateful Dead and Phish have promised him tickets, but that he would need to wait to see if the Senate schedule allowed him to head to Chicago.

Leahy has kept his passion for music while maintaining an industrious schedule as a senator. A staunch liberal, Leahy has been key in fights to reform the immigration system, protect civil liberties and most recently to re-establish relations with Cuba.

His seniority made him third in line of presidential succession until the rival Republican Party took control of the Senate this month.

Leahy's musical tastes have occasionally faced criticism from conservatives who accuse him of condoning the drug use that was so prevalent at Grateful Dead concerts.

To which Leahy replies: "I like Van Gogh's paintings. But I'm not going to cut off my ear."