Pop star Justin Bieber and his mentor, Usher, kicked off with a medley that began with the 16-year-old best new artist nominee on his acoustic guitar, then launching into an amped-up version of his new song, "Never Say Never." Usher, a five-time Grammy winner up for two more awards Sunday, followed with his dance track "OMG."
Both singers were backed by pyrotechnic effects and a stage full of dancers. Bieber's number also featured fire-breathers, twirling gymnasts and an appearance by tiny 12-year-old rapper Jaden Smith.
There were no special effects during Mumford & Sons' performance of their hit, "The Cave." The seven-piece folk band, also nominated for best new artist, played acoustically on a bare stage, followed by fellow folksters the Avett Brothers, who sang their song, "Head Full of Doubt/Road Full of Promise."
String players from the two bands -- guitarists, bassists, a cellist and two banjo players -- joined with other guitarists to back folk icon Bob Dylan, a 10-time Grammy winner who is making a rare appearance on the music industry awards show.
The 69-year-old rocker, who wore jeans, a hoody and a knit cap to rehearsals, let out a guttural voice far larger than his diminutive frame as he sang his 1965 blues track, "Maggie's Farm," backed by a chorus of strings.
Other performers set to take the stage during Sunday's ceremony include Dr. Dre, Rihanna, Eminem, Katy Perry, Barbra Streisand, Mick Jagger and Lady Gaga.
The Grammy Awards will be presented at Staples Center and broadcast on CBS.