Alicia Keys has performed a piano-tinged version of the national anthem that her publicist assured was live at the Super Bowl.

The Grammy-winning singer played the piano as she sang The Star Spangled Banner in a long red dress with her eyes shut.

She followed Jennifer Hudson, who performed America The Beautiful with the 26-member Sandy Hook Elementary School chorus, a performance that had some players on the sideline on the verge of tears.

The children wore green ribbons on their shirts in honour of the 20 pupils and six adults who were killed in the December 14 shooting rampage at their school in Newton, Connecticut.

The youngsters began the song softly before Hudson, whose mother, brother and seven-year-old nephew were shot dead five years ago, jumped in with her gospel-flavoured vocals.

Beyonce balanced out the testosterone levels on the football field with a dance-heavy half-time performance that featured her Destiny's Child bandmates and an all-female band.

She emerged on stage singing some of Love On Top, transitioning to her hit Crazy In Love in an all-black ensemble which matched the dark stage.

She sang live and sounded good, days after admitting miming to a pre-recorded track at President Barack Obama's inauguration.

She had a swarm of background dancers and band members spread throughout the stage, along with videotaped images of herself dancing. She was joined by her Destiny's Child bandmates, Kelly Rowland and Michelle Williams, to sing Bootylicious. But Rowland and Williams were barely heard when the group sang Independent Woman, as their voices faded into the background. They also joined in for some of Single Ladies (Put a Ring On It), where Beyonce's voice grew stronger.

She asked the crowd to put their hands toward her she belted the slow groove Halo on bended knee.