EAST RUTHERFORD, N.J. — As is the wont with Hot 97’s Summer Jam, an annual reckoning of the hip-hop and R&B pecking order, this year’s show at Giants Stadium here on Sunday night essentially came to an end well before the last act finished its set. But in a twist this year the festivities began early — two nights prior, to be specific. All last week the New York radio station known as Hot 97 had been hyping a transformative event: not Sunday night’s five-hour concert but the Friday night premiere of a new song by the not-quite-retired Jay-Z. A listener could have been forgiven for forgetting that there was a show at all.

Hot 97 Summer Jam 2009: Jay-Z, left, and T-Pain onstage at Giants Stadium on Sunday night in an annual hip-hop and R&B show.

Mary J. Blige at Giants Stadium on Sunday night.