When he was seven years old, President Donald Trump punched his school music teacher.

"I actually gave a teacher a black eye," he wrote in his 1987 book The Art Of The Deal, "because I didn't think he knew anything about music."

Mr Trump says he was "almost expelled" over the incident, and it suggests he's as opinionated about music as he is about trade or taxes.

The president is a big fan of The Rolling Stones, Eminem and Elton John (a decidedly one-way relationship), but his favourite song is Peggy Lee's Is That All There Is? It's an interesting choice: Lee's nihilistic ballad essentially says life is a series of meaningless disappointments, so you might as well drink away your sorrows and forget about the rest of the world.

Mr Trump sees it differently. "It's a great song because I've had these tremendous successes and then I'm off to the next one. Because, it's like, 'Oh, is that all there is?'" he told his biographer Michael D'Antonio, in 2014.

So what about his Democratic rival, Joe Biden? Well, his tastes are no more up-to-date. His favourite band is traditional Irish folk outfit The Chieftains, he told People Magazine in 2012, adding: "I would sing Shenandoah if I had any musical talent."

Shenandoah, which The Chieftains recorded in 1998, actually dates back to the early 19th Century. The story of a fur trapper who falls in love with the daughter of a Native American chief, it's steeped in romanticism for the early days of America.

None of these songs have been played on the campaign trail this year - but the candidates' musical preferences at rallies and in advertisements offer a glimpse into what they think works for their supporters.

Trump: Trolling critics

Mr Trump's playlist leans heavily on classic rock songs that project power and combative self-confidence.

He frequently plays Queen's We Are The Champions - whose refrain, "No time for losers," could almost be the president's inner monologue.

Tina Turner's The Best ("you're better than all the rest") and Survivor's pugnacious Eye Of The Tiger ("just a man and his will to survive") fulfil similar functions - conveying the idea of Mr Trump as a lone wolf, fighting the political establishment.

Mr Trump often seems to be trolling critics with his choices. Why else would he play Gnarls Barkley's Crazy, or The Rolling Stones' You Can't Always Get What You Want? And his perceived persecution by the media gets a musical airing, too, through songs like Michael Jackson's Beat It.

"They told him, don't you ever come around here," sings the star, who once kept a home in one of Mr Trump's buildings in New York. "Don't want to see your face, you'd better disappear."

But the song actually advocates retreat. "You'd better leave while you can," Jackson advises, the message being: You think you're tough, but your opponents are tougher... so be the better man and walk away.

Mr Trump's song choices are usually based on how they feel, rather than a scholarly analysis of the lyrics. His pre-speech playlist is designed to keep the audience pumped up. They often stand for hours before he comes on stage, so the focus is on timeless sing-alongs, seemingly targeted at white voters in their 50s and 60s.

That means songs like Elton John's Tiny Dancer and Laura Branigan's Gloria, mixed with rousing classical numbers like Nessun Dorma and the patriotic Battle Of The Hymn Republic (Glory, Glory, Hallelujah).

In recent months, as the president has courted black voters ("I did more for the Black community in 47 months than Joe Biden did in 47 years") he has also started including a few soul classics in his set. James Brown's Please, Please, Please and Barry White's My First, My Last, My Everything were given an airing during last week's rally in Erie, Pennsylvania.

Biden: Earnest decency

Mr Biden's playlist has been almost evenly divided between black and white artists since he announced his candidacy in April 2019.

Recently, his walk-on music has been The Staple Singers' deep cut We The People - an uplifting, soulful hymn to unity, whose title was lifted from the preamble to the US Constitution.

"You may have the black blood / Or you may have the white blood," sing the gospel group, "But we are all living on blood / So don't let nobody slip into the mud."

It's the sort of message Mr Biden has sought to build his campaign around, calling for harmony and stability.

He tends to favour feel-good songs like Bill Withers' Lovely Day or Jackie Wilson's (Your Love Keeps Lifting Me) Higher and Higher. But for those paying attention, there's often a message hidden in the lyrics.

"Powers keep on lyin' / While your people keep on dyin,'" sings Stevie Wonder in campaign staple Higher Ground - a not-so-thinly veiled reference to the Trump administration's handling of the Covid-19 pandemic.

After speaking, Mr Biden usually leaves the stage to the strains of Bruce Springsteen's We Take Care Of Our Own. Like Born In The USA, the song is actually a critique of America, originally written in response to President Bush's handling of Hurricane Katrina.

"There ain't no help, the cavalry stayed home," sings The Boss, who says he's "looking for the map that leads me home". Mr Biden is, presumably, trying to align himself with Springsteen - a working-class hero who's determined to set America back on the right path.
Musical gaffes

But sometimes, the candidates select songs that make you wonder if they've paid attention to the words at all.

What is Mr Trump trying to say when he blasts out Sympathy For The Devil, a song literally written from the perspective of Satan?

And, wonderful though Haim's The Wire is, does Mr Biden realise he's being welcomed onto the stage with the lyrics: "I fumbled it when it came down to the wire"?

Mr Biden suffered another musical misfire last month, when he attempted to woo a large Puerto Rican audience in Florida by playing the Reggaeton song Despacito from his phone, while dancing awkwardly behind the podium (Luis Fonsi, who recorded the song, had just introduced him to the crowd).

As right-wing pundits gleefully pointed out, Despacito is Spanish for "slowly" - a perfect descriptor for the candidate they refer to as Sleepy Joe.

After his brush with Covid-19 earlier this month, Mr Trump has also been keen to prove he's neither slow nor sleepy, and TikTok is awash with memes of him dancing to The Village People's YMCA.

In fact, the president seems functionally incapable of staying still when the song strikes up - pumping his fists back and forth, and lurching from side to side like a priest at a wedding. His supporters have even recorded a new version of the track, where YMCA becomes MAGA.

The 70s disco classic has been part of Mr Trump's playlist since at least last year, but it got bumped up the running order in June when the Rolling Stones threatened to sue the campaign over the use of their song You Can't Always Get What You Want.

They're not the only ones to object: Neil Young, Adele, Aerosmith, Pharrell Williams, Rihanna, Guns N' Roses and Phil Collins have all demanded not to be played at Mr Trump's rallies, with varying degrees of success.
Pop endorsements

The Village People were more relaxed. "Like millions of Village People fans worldwide, the President and his supporters have shown a genuine like for our music," they wrote on Facebook in February. "Our music is all-inclusive and certainly everyone is entitled to do the YMCA dance, regardless of their political affiliation."

Mr Trump also has the endorsement of country star Lee Greenwood, whose sentimental ballad God Bless the USA has been his walk-on music since 2016.

"That made me very proud," Greenwood told the Taste of Country website in 2017. "I love the model 'Keep America Great' and 'Let's make it great again' so I'm all on board for that."

But Mr Trump enjoys very little support from the current crop of pop stars, with Cardi B, Taylor Swift, Lizzo, Frank Ocean and DaBaby all endorsing Mr Biden this year.

And the Democratic candidate has deployed pop music to take down his opponent in campaign ads targeted at younger voters.

One video posted to social media in May featured Mr Trump complaining about his treatment by the press, set to a soundtrack of Justin Timberlake's Cry Me A River.

But in the end, music can only set a mood. Voters won't decide who wins based on the candidates' CD collections.

In fact, a 2016 Ohio survey concluded that star endorsements had no effect on most voters' intentions in that year's presidential race - and some celebrities actually put people off. An endorsement from Beyonce was, apparently, the biggest turn-off.