Fresh off his performance opening the Grammys ’ Premiere Ceremony last week, Trombone Shorty is gearing up for a milestone birthday and concert. Set for Saturday, April 25, the event dubbed “Shorty Turns 40” will celebrate the Grammy-winning New Orleans musician with an array of special guests. What’s more, the party takes place during New Orleans’ signature musical season, that of Jazz Fest. Shorty Turns 40, which coincides with the 10th anniversary of his Treme Threauxdown concert, will take