The Peace Bell will be rung at the United Nations on Monday, Sept. 21, officially commemorating this year's International Day of Peace. The lofty ideal of world harmony has been a common theme for songwriters throughout music history, with particular urgency during the conflict-challenged 1960s and '70s. The fact that there's been a recent resurgence in peace-loving lyrics only means that we're still a long way off from the goal.

'People Get Ready,' the Impressions (1965)

Perhaps the great Curtis Mayfield's best-known song, 'People Get Ready' was chosen as one of the 10 best songs of all time by a Mojo magazine panel that included Paul McCartney and Brian Wilson. Inspired by the historic March on Washington in 1963, the song was Mayfield's pop-gospel version of "I Have a Dream."

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'One Love,' Bob Marley (1977)

The reggae great accentuated his own ode to positivity with echoes of Mayfield's 'People Get Ready.' Such a simple sentiment, and about as eloquent as it gets: "Let's get together and feel all right."

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'Waiting on the World to Change,' John Mayer (2006)

Hotshot John Mayer wasn't exactly known as an activist when he recorded his best-known song, the unabashedly political 'Waiting on the World to Change.' Inspired by Curtis Mayfield, Mayer acknowledged the unfortunate truths that gave him the forum to call for peace: "You cannot avoid war in life, you cannot avoid the fear of terrorism."

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'I Hope,' Dixie Chicks (2005)

John Mayer played guitar on this forward-thinking song, in which the Dixie Chicks envisioned a better world for the next generation. "Thou shalt not kill," the preacher reminds his congregation. The Chicks, emerging from the ugly political fracas over their condemnation of President Bush and the Iraq War, delivered a simple, graceful plea for more joy and laughter for their children.

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'Peace Train,' Cat Stevens (1971)

Despite the weird controversy he's sparked since his Muslim conversion, the folksinger now known as Yusuf Islam was once the very epitome of mainstream pacifism, as this hit single, his first US Top 10, still attests.

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'Love Train,' O'Jays (1973)

Instantly recognizable today as a long-running beer ad, the O'Jays' biggest hit (a No. 1) still retains its significance to multiple generations as a tribute to cross-cultural compassion. From the heart of Philly soul in the City of Brotherly Love to the world powers in England, China, Russia and beyond.

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'Wake Up Everybody,' Harold Melvin & the Blue Notes (1975)

Another product of the Philly soul team Gamble & Huff, this soul-gospel classic was sung with serious conviction by Teddy Pendergrass, then a newcomer to the group. Since he'd been a child preacher, his pop sermon against apathy rang true: "Need some help, y'all!"

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'Higher Ground,' Stevie Wonder (1973)

If the road to peace seems like a perpetually uphill climb, leave it to the beatific Stevie Wonder to lead the way to higher ground. The irrepressible soul man sang it at President Obama's inauguration in January 2009 with special guests Shakira and Usher, and nailed it at the 2004 MTV Video Music Awards with Alicia Keys and Lenny Kravitz.

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'Let Love Rule,' Lenny Kravitz (1989)

Newcomer Kravitz left his paisley heart on his sleeve with the very Beatlesque title track of his debut album. Two decades later, he was still conducting his own peace train, naming his 2008 album 'It Is Time for a Love Revolution.'

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'Give Me Love (Give Me Peace on Earth),' George Harrison (1973)

Though the Beatles recorded several flower-power anthems ('All You Need Is Love,' 'Revolution,' etc.), individual band members probably made their strongest statements about world peace, ironically enough, after the band broke up. George Harrison's serene 'Give Me Love (Give Me Peace on Earth)' was a No. 1 hit for the not-so-quiet Beatle after all in 1973.

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'Imagine,' John Lennon (1971)

No song made a better case for Lennon as a voice of his generation than 'Imagine,' the former Beatle's daydream about a world with no possessions, no religions, no national boundaries -– "nothing to kill or die for." Two years after the song's release, John and Yoko announced their creation of their "conceptual country" of peace, Nutopia.

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'Pride (In the Name of Love),' U2 (1984)

When U2 first went political, they brought onstage an all-white flag like the one conceived by John Lennon and Yoko Ono for their conceptual country, Nutopia. A year or so later, Ireland's most globally active rock band began its long infatuation with American social history with this tribute to the martyred pacifist Martin Luther King Jr.

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'People Got to Be Free,' the Rascals (1968)

Though this hippie classic was released in the tumultuous year of 1968, shortly after the assassinations of Martin Luther King and Robert F. Kennedy, it was actually written in response to an ugly incident the Rascals experienced with some Deep South rednecks -- proving that all politics (of peace) is local.

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'Get Together,' the Youngbloods (1969)

Originally recorded by the Kingston Trio in 1964, 'Get Together' was already well-traveled by the time its iconic hippie-era version was recorded by the Youngbloods three years later. That version didn't become a smash until it was revived as a public service commercial for the National Conference of Christians and Jews: "C'mon, people now, smile on your brother."

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'What's Going On,' Marvin Gaye (1971)

"Brother, brother, brother, there's far too many of you dying," sang the newly politicized Marvin Gaye on the title track of his stone masterpiece, released in 1971. Sing it, Brother Marvin: War is not the answer, only love can conquer hate.

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'(What's So Funny 'Bout) Peace, Love and Understanding,' Elvis Costello (1979)

Nick Lowe wrote this song in the mid-1970s for his influential pub-rock band Brinsley Schwarz. It's best known, however, in a later version by post-punk's angry young man, Elvis Costello (which Lowe produced). Where is the harmony? the song asks. These two song craftsmen have always known.

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'I'd Like to Teach the World to Sing,' the New Seekers (1971)

... in perfect harmony. Best remembered as an ad for a certain cola company, the song was so popular that it was hastily recorded by the New Seekers, who had turned down an offer to record the song for the commercial in the first place. A huge worldwide smash, the song demonstrates that peace, love and understanding is a concept well worthy of its own commercial jingle.

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'We Are the World,' USA for Africa (1985)

Famine was the specific cause that inspired the historic gathering of pop superstars known as USA for Africa, but the group's signature song, written by Michael Jackson and Lionel Richie, worked as an all-inclusive plea for peace and brotherhood. The difficult assignment of individual lines to the star contributors was, said producer Quincy Jones, "like putting a watermelon in a Coke bottle."

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'War,' Edwin Starr (1970)

Originally recorded by the Temptations, one of Motown's biggest acts, the protest anthem 'War' was deemed a little too polarizing to be released as a single. But everyone at the label recognized it as a powerful song, and second-tier Motown singer Edwin Starr volunteered to record his own version. A smash hit at the height of the Vietnam debate, the song scaled the charts again in a 1986 version by Bruce Springsteen.

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'21 Guns,' Green Day (2009)

A centerpiece of Green Day's concept album '21st Century Breakdown,' this stately ballad calls for peace on a personal level: "Lay down your arms, give up the fight." As that straight-edge punk called Gandhi once said, "Use truth as your anvil, nonviolence as your hammer."