The concept of “performative composition,” guided by his conducting experience, leads Gustav Mahler to implement variable tempo design as a formal principle in the first movement of his Ninth Symphony (1909–10). The Schoenberg student and conductor Erwin Stein, who held Mahler’s conducting in high esteem, argued that the movement’s tempo design, that is, the various tempi employed throughout the movement’s sections, should be oriented toward the main tempo (Andante comodo). A review of comments on this principle by Theodor W. Adorno, Bruno Walter, and Nicholas Cook is complemented by record-ings of the movement by Walter, Leonard Bernstein, and Michael Gielen in a comparative study of over 100 recordings from 1938 to 2019 with respect to tempo design and “performative form.”