A change has also come over Voigt's voice lately, though it's hard to tell if it's from weight loss or normal aging—controversy still rages over whether Maria Callas's drastic diets contributed to her rapid vocal decline. Not that Voigt as yet exhibits any of Callas's technical problems: Her voice continues to be reliably supported and under control. What is noticeable, however—earlier this season in Verdi's La Forza del Destino and now in Tosca—is a marked thinning of quality at the very center of the instrument, together with a slight acidity and tightening of the tone that has definitely taken the youthful bloom off, especially at the top.