document: Kanye West was supposed to have an album ready for his (divisive) headline performance at Glastonbury - but the record, at first titled So Help Me God, then renamed SWISH, has failed to materialise.
  Fans even petitioned the White House to get it released - but hope is on the horizon. Ten days ago, the star tweeted "I'm finishing my album"
  He wasn't the only one dragging his sequinned heels. R&B star Frank Ocean's follow-up to the groundbreaking Channel Orange was scheduled for July, then disappeared - prompting a foul-mouthed outburst from Adele.
  And Rihanna held a lavish launch party for her eighth album, ANTI, in November - but has subsequently failed to produce any new music. In fact, the Bajan star is still auditioning new material, songwriter Sia told BBC Radio 2 a fortnight ago.
  "The other night she came over and listened to half of 25 songs I played her because she's still looking for songs for her new album," said the songwriter, who previously wrote Rihanna's number one single, Diamonds.
  "It was a business meeting for sure. She took four [songs], but I don't know if they'll end up [on the album]."
  Rihanna kicks off a world tour, ostensibly in support of ANTI, in February - but don't assume we'll get new material before the opening night.
  "Every album needs to be an 11 out of 10 these days because the reviews are instant," one music industry executive told BBC News.
  Agenda-setting releases from Kendrick Lamar, Adele and Dr Dre sent pop stars scrambling into the studio to improve their records this year - so don't expect Rihanna, Kanye or Frank to release anything until they're sure they'll make a similar impact.
  Less timid is David Bowie, whose 25th album â˜… (Blackstar) was directly influenced by Kendrick Lamar's expansive take on jazz, hip-hop and funk on the 11 times Grammy-nominated To Pimp A Butterfly.
  Assembling a crack team of nimble-fingered jazz maestros, the aim was "in many, many ways, to avoid rock and roll," producer Tony Visconti told Rolling Stone magazine. It comes out on 8 January- Bowie's 69th birthday.
  Travelling in the other direction is Elton John, whose Wonderful Crazy Night is a return to the rollicking rock sound of his 1970s heyday, inspired by his domestic bliss.
  "I wanted to do something joyous because I was so happy with my children and my husband," the star told the BBC.
  Also lining up new releases are Gorillaz, whose new album will be "really fast," with "a lot of energy," says Damon Albarn; and Katy Perry, who promises a new direction on her fourth album. "I can't keep topping myself because I'll just combust at some point," she told the Associated Press.
  Primal Scream, who headline the 6 Music Festival in February, have teased six seconds of their 11th album Chaosmosis, on YouTube; while R&B band TLC are working on a fan-funded new album - their first since 2002's 3D.
  Will it include another Waterfalls or No Scrubs? Who cares, when contributing to the recording costs can earn you a "TLC slumber party" with T-Boz?
  Pop star Lorde has been in the studio since March working on the follow-up to her debut, Pure Heroine - but she has warned fans: "I'm taking my time to make the new stuff as good as I can."
  PJ Harvey has also been biding her time. She allowed fans to witness the creation of her new album in a public art installation earlier this year but the results have yet to see the light of day.
  And if you're interested in new music, check out multi-instrumentalist Jack Garratt, who cherry-picks sounds from rock, pop, dubstep and electronica, with his soaring vocals the sole connective tissue.
  He's already won the Brits Critics' Choice award, and is on the longlist for the BBC's Sound of 2016.
  Other artists in the running include indie-rock quartet Blossoms, Afrobeat-inspired rapper J Hus and Canadian singer Alessia Cara, who recently cracked the US top 10 with her anti-party anthem, Here.
  Outside the BBC's influential list, newcomers to watch include Frances, whose wistful piano ballads will appeal to fans of Adele, and soul singer Jones - whose single Indulge was one of the steamiest records of the last 12 months.
  Other artists preparing new albums include:
  The hottest ticket for 2016 is Adele, whose tour kicks off in Belfast on Leap Day; while 2015's comeback king Justin Bieber has sold out six night's at London's O2.
  Coldplay start the year at the SuperBowl before heading off to visit the world's biggest enormodrones; while Muse are playing "in the round" for the first time on their ambitious Drones tour, in support of their album of the same name.
  Singer Matt Bellamy told BBC Radio 2 the show would feature "a whole swarm of drones" flying over the audience. Hopefully they won't slice anyone's fingers off, Enrique Iglesias-style.
  At the other end of the musical spectrum, Little Mix will be hitting arenas across the UK with their Get Weird tour. "The way it opens is just epic," Jesy Nelson told the BBC - but the band wouldn't spill any more beans.
  "It's all a surprise," said Perrie Edwards. "You'll have to get tickets if you want to know."
  Film composer Hans Zimmer is staging his first tour, performing music from Inception, Gladiator, The Dark Knight trilogy and The Lion King to name a few. But we're mainly hoping he'll resurrect his finest moment - the theme song to Going For Gold.
  Queen are reuniting with Adam Lambert to headline the Isle of Wight Festival, while Tears For Fears are a wily booking for Camp Bestival.
  Glastonbury has yet to announce its headliners, but Adele, AC/DC and Muse are said to be in the running. David Bowie has also been rumoured - more out of tradition than expectation - while Rihanna has a Glastonbury-sized gap in her touring schedule, after playing Wembley Stadium earlier in the week.
  I wonder if she'll have finished her album by then?
summary: The past year was when the planet's biggest pop stars went missing in action.