Sir Elton John and Glee star Naya Rivera have added some star power to a new album by classical act 2Cellos.

The Croatian-Slovenian duo, real names Luka Sulic and Stjepan Hauser, were personally picked by the Rocket Man to join him on tour in 2011 after he watched their cello-only cover of Michael Jackson's Smooth Criminal on

Now the pair has hit the recording studio with Sir Elton, who provides the vocals for a cover of Fleetwood Mac's Oh Well on their upcoming release, In2ition.

Recalling his first chat with their idol, Sulic tells, "I was so nervous and shocked. But the minute we started speaking he was so supportive. Ever since we met him, he's been amazing support for us and great fun. So generous, he's giving so much to everyone. He supports young musicians."

Acclaimed pianist Lang Lang, pop star Sky Ferreira and rocker Steve Vai also appear on the album, while actress Rivera sings on their cover of Muse's Supermassive Black Hole.

In2ition is due to hit shelves in March (13).