Robert Johnson: If you'll forgive the morbidness, Robert Johnson was arguably the inaugural member of the 27 Club. Nowadays, he's cited as an influence by the likes of Eric Clapton and Robert Plant, but during his lifetime, he played mostly on street corners and in juke joints. It was only after the reissue of his 1936 recordings 30 years after his death that his work reached a wider audience. The cause of his early death is unknown, but has been the subject of wild speculation - the most noteable of which is that he sold his soul to the devil to achieve success.
Rodriguez: After releasing two poorly-selling albums in the 1970s, the American folk musician's career initially proved short-lived. Unbeknownst to him though, his albums became hugely popular in South Africa - outselling those of Elvis Presley. There, it was widely believed that Rodriguez had committed suicide. In the 1990s though, two determined fans managed to track him down, which led to an unexpected (to him more than anyone) revival of his career. A second revival came in 2012 when the documentary Searching For Sugar Man, which detailed this search, won an Academy Award.
William Onyeabor: After self-releasing eight albums between 1977 and 1985, the Nigerian funk musician became a born-again Christian and refused to ever speak about himself or his music again. His legacy and popularity only grew from this though, and in 2014 he granted 6 Music's Lauren Laverne a radio interview - his first ever - during which he admitted that he's never played live, but plans to release new music soon. Watch this space.
Burial: After rumours began circulating that the electronic musician was in fact an alter-ego of Aphex Twin or Fatboy Slim, William Bevan decided it was time to reveal his identity in 2008. He did so in the form of this grainy MySpace picture, and in the seven years since has revealed just one more photo of himself.
Neutral Milk Hotel: Neutral Milk Hotel's Jeff Mangum, to be specific. Mangum rarely gives interviews, frequently disappears for years on end, and rarely plays live. In 2012, he ended the touring drought with a surprisingly extensive tour, during which he barely spoke and sported a faintly resembled a post-Vietnam Lieutenant Dan from Forrest Gump.
Ghost: There are many bands who wear masks on-stage and attempt to keep their identities a mystery. Few do so as successfully as this Swedish heavy metal band. Despite gaining a fervent fanbase, the members are referred to only as Nameless Ghouls, and their identity is completely unknown. The closest they've come to revealing the secret was in 2013, when they started to reveal their membership to their local friends and family "for house peace." Fair enough.
The Avalanches: Just one album every few decades is enough for The Avalanches. Perhaps just one album ever. The band released their debut, Since I Left You, in 2000 - and are said to have been working on its follow-up since 2005. That's a decade. In that time, various members have left and re-joined, and the album's release has been teased around 147 times. It's still yet to materialise.
The Residents: Depsite having released over 60 albums over the last 40 years, the avant-garde music collective operate under anonymity. During public appearances, the remain silent and usually don tuxedos, eyeball helmets and top hats. Much of the speculation revolves around their management team, The Cryptic Corporation - with many fans assuming the management team and the band to be one and the same. They've repeatedly denied this.