In the famous Preface to Alceste, Christoph Willibald Gluck and his librettist Ranieri de' Calzabigi posited a new direction for opera. They spoke of moving beyond Baroque forms, of striving for a new naturalism in opera. They wanted, in Calzabigi's words, to ''liberate the language of the heart.'' Taken from the height of this Reform period, the arias on Che pur ciel reveal composers exploring and experimenting, at struggle and at play, as they create the new forms that bring to opera the noble simplicity of the Classical era. The remarkable countertenor Bejun Mehta is the featured soloist, accompanied by the Akademie fur Alte Musik Berlin led by Rene Jacobs.