Gradual

Gradual an anthem, psalm, or part of a psalm chanted in the mass between the epistle and the gospel. So called because the chanter stood on the pulpit steps. The name is also given to the book containing the psalms chanted at mass, which was called gradale, or graduate. — Palmer, Orig. Liturg. 2:46; Procter, On Common Prayer, pages 8, 317.