 He is credited with the invention (or at least the introduction into Orthodox liturgical services) of the canon, a new form of hymnody.Previously, the portion of the Matins service which is now the canon was composed of chanting the nine biblical canticles, with short refrains inserted between the scripture verses.Saint Andrew expanded these refrains into fully developed poetic Odes, each of which begins with the theme (Irmos) of the scriptural canticle, but then goes on to expound the theme of the feast being celebrated that day (whether the Lord, the Theotokos, a saint, the departed, etc.