While others in Nashville were staring at the clock on New Year’s Eve and chanting “10 . . . 9 . . . 8 . . . 7,” Brad Paisley, Bill Anderson and a few of their friends were sitting on the stage of the Grand Ole Opry House, looking out at the empty seats and singing songs and telling stories to each other. This coolest of all jams took place after the Friday night Opry was over and most of the other performers on the show had gone home. Paisley had returned from Christmas break in his hometown of Glen Dale, W. Va., to guest star on the Friday and Saturday night Opry shows. Still riding high on his first No. 1 hit, “He Didn’t Have to Be,” Paisley counts the spontaneous New Year’s Eve gathering among his most treasured moments.