Twentieth-century Mexico saw major musical transformations: the expansion of radio and records, new cultural institutions, the circulation of popular music, and experimentation in composition. Recordings trace changes in studio techniques, commercial formats, regional practices, and listening habits. The period encompasses very different scenes and communities and should not be treated as one homogeneous style. This category organizes materials connected with the twentieth century and helps distinguish a work composed then, a recording made during those decades, and a later reissue. Catalogue dates and edition notes are essential for interpreting each case and understanding the surviving sound document.