In 1936 Canon Ascanio Andreoni of the Cathedral Chapter and Rector of the Milanese Seminary of Venegono, discovered the (high) competence of Maffeis the organist and offered him the chair of piano, harmonium and organ in the religious institute which he directed.
Nothing could have been more exciting for the musician: besides having a secure job, in the Seminary he would have the opportunity to be introduced into the environment frequented by the greatest exponents engaged in the search for new musical forms more appropriate to the needs of the liturgy than the shoddy music too often imitating melodic arias from melodramas.
Thus he became part of the group of composers inspired by Andreoni, which would take the name of Cecilian Movement.
Among these were his first model, Donini, then Perosi his close friend, Pozzoli his professor, Ramella, Spinelli, Chiesa and others. Motivated by the aims of the Cecilian Reform, he composed his first sacred music.