Joss Stone has spent most of her career trying to convince listeners that she’s a major artist, even while she’s also tried to convince listeners that’s she’s a major star. In both cases, she’s gotten by on her voice, which is irrefutably remarkable, and her self-confidence, which is almost as strong. Simply by acting like a major star—right down to the frequent self-mythologizing—she’s managed to amass some substantial credibility and fame. That’s not to say that she’s entirely undeserving—her voice truly is a unique and powerful instrument, especially in this day and age where the likes of Rihanna and Ke$ha can be lauded as “singers”. Still, there’s always been an asterisk around her career, one that always overshadows even the best of her work. The Best Of Joss Stone: 2003-2009 not only doesn’t smooth out this uncertainty, it actually emphasizes it.

The album compiles all of Stone’s biggest singles from the four albums she recorded for Virgin/EMI, and throws in a cover of Nat King Cole’s “L-O-V-E” she recorded for a commercial. Sequenced chronologically, it has all of the songs she’s most known for assembled in a package that’s meant to cement her status as a major artist. What the collection actually does, however, is underline the contradictions that have always made Stone’s work so difficult to embrace. Stone has a fine voice but she doesn’t seem to actually live or feel her songs. She just sings them with uncanny technical precision. On a song like “Spoiled” (from 2004’s Mind, Body & Soul), she doesn’t sound like a world-weary soul diva with a heart broken from years of shattered love—she sounds like what she is, a teenager (Stone was all of 17 when she recorded the album) hitting the notes precisely but without fully understanding their emotion. Then again, how could she, really? For her, the song sounds like an exercise rather than an exorcism, and while that doesn’t make it bad or unlistenable, it also belies the notion that this is music she’s always meant to make from the bottom of her heart. She’s not exactly a poseur, but one thing that emerges as you listen to this compilation is that she’s also not nearly the fully formed soul diva she’s been so eager to present herself as.

The compilation also demonstrates Stone’s frequent self-redefinitions, from her beginnings as a classic soul singer to her attempts to become more of a mainstream dance-pop artist. What emerges, however, is equally as confusing. Having begun her career as an old-school soul singer with songs like “Right to Be Wrong” and “Super Duper Love”, she gradually morphed into a standard-issue R&B/pop singer with Introducing…Joss Stone, the 2007 album that included collaborations with the likes of Common. This could conceivably be considered artistic evolution, except that Stone made it a point repeatedly in interviews to proclaim that her old-school soul diva phase was her genuine artistic personality and that she had to fight hard to prevent her record label from turning her into Christina Aguilera redux. What the presence of her later more pop/R&B oriented songs highlights is just how uncertain her career is. With their generic dance/hip-hop beats, songs like “Tell Me What We’re Gonna Do Now” and “Tell Me ‘Bout It” have absolutely nothing in common with Stone’s previous old-school songs. Moreover, the contrast is so jarring that it doesn’t sound like an artistic evolution—it sounds like someone grasping for a creative identity. When you hear all the hits sequenced together here, you realize just how disjointed her career really has been.

None of this would matter much if Stone was simply another fame-hungry pop tartlet with pedestrian talents. Or, in other words, if she was Ke$ha or Rebecca Black. Stone’s voice, however, makes this a far more disheartening story. Her voice is truly stunning—it’s a rich, smoky instrument that is never less than captivating. The problem is that she frequently doesn’t seem to know when to not use it so heavily. Stone’s cover of Nat King Cole’s “L-O-V-E”, recorded for a Chanel commercial and included here, is especially overwrought, particularly for a song that’s meant to be breezy and lightweight. It’s not an accident that the best songs compiled here, like the more recent “Free Me” (from Colour Me Free) are the ones where she tones down the mannered vocal gymnastics and just sings, simply and evocatively. Again, all of this could be chalked up to her youth and inexperience; clearly, she needed to develop the confidence to learn when to tone down her theatrics. Still, much as with her wobbly genre-jumping, it’s another indication that, contrary to her oft-stated sentiments, she did not emerge as a fully-formed artist ready to take on the world.

The collection does not include any songs from 2011’s LP1, recorded for another label, but at least her more recent work (“L-O-V-E” notwithstanding) demonstrates that she may have finally found a style and sound that suits her. It would, after all, be a shame if audiences never give her another chance. Her excessive over-singing, coupled with a frequent inability to decide on a compelling persona and stick with it, make her career one of the most frustrating and disappointing in modern music, but she still has potential for more. Up to now, unfortunately, it’s been easy to dismiss her music as nice soul for pretty people—songs that sound great while playing at the nearby Abercrombie & Fitch (or is that Tommy Hilfiger?) store, but ones that wilt considerably when you put them next to the likes of Aretha Franklin. The Best of Joss Stone doesn’t resolve these issues—it highlights them. Hopefully, however, it also points the way for a more satisfying future direction.

• Multiple songs Last.fm