Moving past the tragedy of Verdi’s Rigoletto, the Atlanta Opera changed gears and delighted audiences with performances of Mozart’s masterpiece “Le nozze di Figaro”, and the company should pride itself in the big success that it proved to be. The dimensions of the piece, though a mainstay of the standard repertoire, are surely daunting for any company: It is a very long opera with a large cast, filled with sprawling dramatic complications and musical pitfalls. Thus it was to the Atlanta Opera’s credit that so much of this presentation struck the right chord, and between the hours of 8 pm and midnight on the performance of April 10, there were many long stretches of time where Mozart lived. The credit belonged to a rather unlikely cast comprised of both young and veteran singers, who were able to bring forth the score’s vitality through their elegant declamation.