Whenever I've seen a music icon in concert - stars who've been around for decades, who've helped to shape pop and rock with landmark albums, whose body of work will outlive them - part of me is lost in wonder. I've learned that you can enjoy the music, and the live experience, all the while thinking about the performer's storied achievements.

I've had that train of thought while watching people such as Roger Waters, and Bob Dylan, and Neil Young, and Paul Simon, and Paul McCartney, and Prince, and many others. And a few years ago - December 2015, to be precise - I experienced it again as Madonna's Rebel Heart concert got underway at the SSE Hydro.

Music review: Madonna at SSE Hydro, Glasgow

It was a captivating show, with stunning visuals, but from time to time I caught myself reflecting about Madonna, about the different stages of her career and about all we know of her, starting with the carefree days of Desperately Seeking Susan, her trendsetting sense of fashion and the joyous early hits such as Holiday, Like A Virgin, Material Girl, Into the Groove. It's hard to forget, now, the extent to which Madonna dominated the Eighties, alongside Prince and Michael Jackson. This was, to borrow an expression coined by the Pet Shop Boys, her imperial phase.

The Herald: Madonna on stage at the SSE Hydro, December 2015Madonna on stage at the SSE Hydro, December 2015 (Image: Colin Mearns)

Later, much later, came a bolder, more confrontational, more assertive Madonna, the one who mimicked sex acts on stage, who defiantly challenged our ideas about religion and sex, who continued to go her own way, on stage and off. The Erotica album, released in 1992, was a game-changer for Madonna in its harder-edged urban sound and its uninhibited sexual content. No wonder the CD case bore a sticker that read: "This version contains language that some people might find offensive".

The Herald: A fan at Madonna's concert at Murrayfield stadium in 2012A fan at Madonna's concert at Murrayfield stadium in 2012 (Image: Stewart Attwood)

The album, which was accompanied by Sex, a shrink-wrapped book of photographs, is, in the words of The Quietus music website, the key in the Madonna discography that unlocks the entire conundrum of who she is as an artist. "Without Erotica, there wouldn’t have been those later big-hitters like 1998’s Ray of Light or 2000’s Music, records which were billed as pop and trailed by a trove of hit singles but were really built on the same sort of restless experimentation she first flirted, nay, cavorted with on Erotica".

In Pictures: Material Girl Madonna through the decades

Without Erotica, it adds, "we wouldn’t be talking about Madonna’s depth in pop in the same way, where she infused her radio-ready melodicism with R&B grooves, hip hop rhythms, and offbeat instrumentation". It also helped pave the way for her long-term career as a unique pop artist.

The Herald: Madonna poses at the MTV Video Music Awards on September 14, 1984 in New York's Radio City Music HallMadonna poses at the MTV Video Music Awards on September 14, 1984 in New York's Radio City Music Hall (Image: AP)

Further albums have followed: the superb Ray of Light, Music, American Life, the excellent Confessions on a Dance Floor, Hard Candy, MDMA, Rebel Heart, and Madame X.

The Herald: Madonna stumbles while performing on stage as her cape is pulled during the 2015 Brit Awards at the O2 Arena, London Madonna stumbles while performing on stage as her cape is pulled during the 2015 Brit Awards at the O2 Arena, London (Image: Yui Mok/PA Wire)

If sales of her albums have fallen sharply from her peak, the clamour for tickets for her world tours have if anything become more remarkable, as seen in the startling speed with which tickets were snapped up for her Celebration tour, an exercise intended to mark her four decade-long recording career. Madonna's recent illness  - she suffered a serious bacterial infection - has caused the postponement of the North American section but the tour is currently scheduled to kick off in Europe in October.

It's hard to believe that Madonna turns 65 tomorrow, August 16. She has been around forever, one of the biggest pop stars ever, and certainly the best-selling female artist of all time. 

As Mary Gabriel, author of a forthcoming biography of Madonna, argues in the New York Times: "During her 40 years in the spotlight, [Madonna] has been loved and loathed in equal measure. It is safe to say no other artist of her renown stirs such passionate debate. At the heart of it lies a basic misconception as to who she is.

"Though she is most often described as such, Madonna is not merely a blinding blue star in a vast celebrity galaxy. She has accomplished what few artists — and even fewer female artists — have done: She has changed the world".

The Herald: The front cover of Madonna's 2015 album, Rebel HeartThe front cover of Madonna's 2015 album, Rebel Heart (Image: PA Photo/Handout)

Madonna, adds Gabriel, has become a cultural wrecking ball, one "who has dared to be everything — performer, songwriter, producer, actor, director, children’s book author, muse — at a time when women were encouraged to stick to one lane. She has broken through social barriers, too, using her words and her work to confront the music industry, Hollywood, the Taliban, the Putin regime and the Vatican, to name just a few of her adversaries, over sexism, misogyny, racism, homophobia and hypocrisy".

The Herald: Madonna performs at the 57th annual Grammy Awards on Sunday, February 8, 2015, in Los AngelesMadonna performs at the 57th annual Grammy Awards on Sunday, February 8, 2015, in Los Angeles (Image: John Shearer/Invision/AP)

Watching Madonna that December night in 2015 was a really interesting experience, for so many reasons: her long run of hits, her constant reinventions, the kaleidoscope of musical approaches she has experimented with, her marked influence on younger female artists.

As the Herald's arts editor, Keith Bruce, remarked in his five-star review: "Some of you perhaps thought the Queen of Pop was the girl who wouldn’t grow up, and was still out to shock and trade provocations with lasses less than half her age. Wise up, because the Rebel Heart show is the work of a woman who has shown no inclination to compromise over 30 years of work and would like to remind us of that".

The Herald: Madonna at Murrayfield, July 2012Madonna at Murrayfield, July 2012 (Image: Stewart Attwood)

Right at the end, it was reported in Rolling Stone magazine, "the venue cut the power to the stage and raised the house lights with one song left in the encore. Rather than ending the gig prematurely, a Santa hat-wearing Madonna and her team of dancers performed “Holiday” sans electricity – even her microphone was shut off – and turning the arena into a giant sing-along".

Madonna took to Instagram to hit out at the venue, saying, “We don’t stop till its over Glasgow! Don’t try to silence the queen". It's worth pointing out, though, that the Hydro said in a statement: “Madonna finished her agreed set, and then chose to come on for another song.  By that stage all the power and control equipment had already been disconnected by her own production engineers.  I would stress that this was not a venue decision".

Madonna's Hydro show had started later than many fans expected - an issue that had arisen at her debut gig north of the border, at Edinburgh's Murrayfield stadium, in July 2012.

Review and pictures: Madonna performs at Murrayfield

As our reviewer, Marianne Gunn, noted, Madonna was displeased with the city's curfew too, with two songs having to be scrapped in order to bring the show in on time. Wrote Gunn: "As the hydraulics lowered her for the final time, her gasped 'We made it!' sounded full of relief as if the whole evening had been a bit of a race against time for the star who will turn 54 next month.

The Herald: Madonna with Guy Ritchie in 2008. The couple married at Skibo Castle in December 2000. Madonna filed for divorce in October 2008, citing irreconcilable differencesMadonna with Guy Ritchie in 2008. The couple married at Skibo Castle in December 2000. Madonna filed for divorce in October 2008, citing irreconcilable differences (Image: Ian West/PA)

"Madge is reputedly a lady who gets what she wants, so to cut short her set to comply with the authorities was about as big a compromise as she makes. The abruptness of how she closed the show could have been remedied by a prompt start, as her show started 45 minutes after the advertised time".

During that show, incidentally, Madonna briefly touched on the subject of the last time she had been in Scotland, for her wedding at Skibo Castle in December 2000, to film director Guy Ritchie, saying: "Let's hope this visit has a more beautiful ending".

The Herald: Madonna, pictured earlier this yearMadonna, pictured earlier this year (Image: PA)

An interesting take on Madonna comes from author Peter Doggett, in Electric Shock, his history of pop music. Despite lacking any of the qualities on which musical fame had once depended, he wrote, Madonna became arguably the most important pop performer of the last thirty years. In place of traditional artistic values, she offered a rival set of coinage, which rapidly became the standard currency of global celebrity.

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"Her assets were an instinctive command of visual style; a shameless self-confidence, and a total belief in her power as an icon. More than any previous pop performer, she transcended music ..."

The Herald: Madonna, in conical bra, performs to a crowd of 74,000 fans at Wembley Stadium in July 1990Madonna, in conical bra, performs to a crowd of 74,000 fans at Wembley Stadium in July 1990 (Image: PA)

Madonna's ambition and generational talent have taken her to an exalted position. But she has not forgotten what it was that drove her, back at the very start of her career. “First of all, I wanted to make a living. I was tired of being broke", she told the New York Times magazine four years ago. "But second of all, all I wanted was a song to get played on the radio. That’s all I was praying for. One song.” 

madonna.com