Countless artists have fueled their early ambitions with dreams of fame and fortune, and experienced the intoxicating thrill of knowing their art commanded the attention of millions, only to see it all crumble when -- for whatever reason -- their work stops resonating. It's an inscrutably complex relationship, this symbiosis between creator and consumer, and it's one that sustains the work while fundamentally altering the creative dynamic. Your favorite rock stars probably don't know you by name, but they know you're out there, and they know they need to keep your attention.

In fact, although a lot of rock writing approaches music as though it's a mode of top-down, one-way expression, it really isn't; no matter how personal or insular a song might be, at some point, the artist is going to think about his audience. We create to communicate, we distribute to be heard, and we repeat the process in order to be understood. Even before the audience exists, the artist is trying to engage it on some level, whether it's subconscious or overt -- and although the biggest acts tend to behave as though they're above that kind of neediness, that's rarely entirely true.

The guys in U2 are more or less alone among their peers when it comes to being utterly open about their quest to maintain a grip on their audience.

Love them or hate them -- and at this point, reactions seem about as mixed as ever -- the guys in U2 are more or less alone among their peers when it comes to being utterly open about their quest to maintain a grip on their audience. During the protracted gestation period for their latest release, 'Songs of Innocence,' singer Bono repeatedly told interviewers that the band worried about remaining relevant at this stage in their career, and they toiled for years over the tracks that eventually surfaced as part of the biggest promotional stunt of 2014.

It's impossible not to admire their honesty, but it's just as hard not to hear the sound of reaching on 'Songs of Innocence' -- it's audibly the work of a band trying to reach the biggest possible audience. There's a certain arrogance there, lurking behind the idea that if the world could just hear what you're up to, of course they'd love it -- but there's also more than a whiff of desperation, and it's just the latest byproduct of U2's ongoing effort to make sense of the global superstardom that erupted around them after 1987's 'The Joshua Tree.'

They were big before that record, of course, and from the opening sounds of their debut, they were clearly a band straining for greatness on a global scale. But you don't release an album that sells 25 million copies worldwide without it altering you somehow, and in U2's case, everything they've done since has been an attempt to challenge, cajole, or outright cater to anyone who ever bought a copy of 'The Joshua Tree.' It's their catalog's touchstone as well as its albatross.

This is not to say that U2 haven't made plenty of entertaining music since 'Tree' hit; it's simply to place subsequent efforts in context. They used their late '80s clout to pull off a multimedia passion project ('Rattle and Hum') before kicking off the '90s with a brilliantly mainstream vanguard effort ('Achtung Baby') that presaged a period in which they tried to distance themselves from the widescreen sepia sonics of their greatest hits ('Zooropa' and 'Pop'). Having covered all that ground, they've spent the last 15 years simply being U2, to varying degrees of success; 2000's 'All That You Can't Leave Behind,' 2004's 'How to Dismantle an Atomic Bomb,' and 2009's 'No Line On the Horizon' are all just as starkly earnest and anthemic as you might expect if you'd somehow managed to miss everything they'd put out over the previous decade.

But where the band's first seven records boasted big music borne on colossal ambition, their more recent efforts sound like the work of musicians waiting for validation -- like U2 is a marketing research group and the world is its focus group. It can produce slickly entertaining stuff, and 'Songs of Innocence' is no exception, but there's a disconcertingly hollow note in the middle of it all; the band's best work binds harrowing intimacy to arena-sized arrangements, and that intimacy has largely gone missing. 'Innocence,' with its deeply autobiographical lyrics, proves a particularly vexing example of how an artist can rely on personal details without revealing enough.

At the other end of the spectrum lies Robert Plant, an artist who knows a thing or two about superstardom -- and who also has a new album out at the moment, a globetrotting sonic patchwork he's dubbed 'lullaby ... and the Ceaseless Roar.' Like most of Plant's work, it evades the expressly personal, but it also might be his most intimate collection, due in no small part to the impression it gives of an artist who's learned to balance the demands of his legacy against the yearnings of his muse.

It's worth mentioning that Plant's career perspective has been at least partly shaped by the losses he's weathered in his personal life, including the sudden death of his young son, Karac, in 1977 and Led Zeppelin drummer John Bonham's passing three years later. By the time he embarked on his solo career with 1982's 'Pictures at Eleven,' Plant had an uncommonly sharp understanding of how fleeting fame -- and life -- can be, and perhaps as a result, he's used his record contracts as a license to do essentially whatever he likes.

Of course, it obviously helped that Plant was already ungodly wealthy from his days in Led Zeppelin, and that his instincts were always fairly commercial; even when he did something mildly subversive, as with 1984's 'Honeydrippers' EP of '50s covers, the results tended to be eminently radio-friendly. But being at peace with his illustrious past no doubt contributed to his ability to avoid some of the many pitfalls suffered by his peers during the occasionally clownish '80s -- if not all of Plant's solo stuff has aged well, none of it is outright painful or embarrassing, either.

And as Plant's sales started to recede from multi-platinum levels, he didn't flail for the brass ring; in fact, starting with 2002's 'Dreamland,' he's made a point of putting out records that sound like they might have been made purely for the enjoyment of the musicians in the room. He's graduated into full-on elder statesman status along the way, shedding his rock god skin and emerging as a sort of stubble-chinned elf who's just as likely to cut a Grammy-hogging covers album with Alison Krauss as he is to start a new band and lead them off in search of fresh musical spoils.

With 'lullaby ... and the Ceaseless Roar' in particular, Plant's approach stands in stark contrast to an album as meticulously prepared for the mainstream as 'Songs of Innocence.' It's a set of songs that sounds unencumbered -- from genres, certainly, given the way it weaves traditional and original songs into a patchwork quilt of acoustic and electronic sounds borrowed from around the world, but also from Plant's own past. Although elements of his previous efforts necessarily remain, it doesn't really sound like anything he's done before, and neither does it sound like a reaction against those albums. It's the sound of an artist aging gracefully while guarding the spark that made him want to make music in the first place.

It'd be refreshing to hear U2 make an album that sounds like the one they wanted to record, rather than one composed with relevance in mind.

It'll be interesting to see how U2's 'Songs of Innocence' gambit plays out, and how the band's inner circle ends up viewing the chasm between the number of free streams and downloads the album racked up (reportedly between 25-80 million) and how many copies it sold traditionally (first-week sales of 28,000 -- roughly equivalent to what Plant sold with 'lullaby'). Accustomed as they've grown to their status as one of the world's biggest bands, it'd be refreshing to hear U2 make an album that sounds like the one they wanted to record, rather than one composed with relevance in mind.

And if they're looking for pointers, placing a phone call to Plant might not be a bad way to start.

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