Is Amanda Seyfried a good singer or in the movie Mamma Mia was her voice altered?

Amanda Seyfried is a talented actress and has demonstrated her singing abilities in several movies, including the Mama Mia franchise. In the first Mamma Mia film, her character Sophie sings several songs, and Seyfried's real voice was used for these performances. She also sang in Les Misérables, where her voice was praised for its strength and clarity.