 In 1769, Gluck adapted the role of Orpheus in his "Orfeo ed Euridice" for Millico to perform at Parma — the original role, composed for the alto castrato Gaetano Guadagni, was transposed up for Millico's soprano voice and the whole opera turned into an act of the celebratory work "Le feste d'Apollo".In 1770, Millico sang, in the Vienna revival of "Alceste", the originally tenor role of Admetus, which Gluck had specially rewritten for him, and created the role of Paris in the same composer's "Paride ed Elena", the last in the trilogy of his Italian reform operas.