“The God with the elephantine visage I shall never forget – Shankara’s son, with massive belly and the thodu in His ear, the Lord who gave his grace to Indra, and of whom mantra is his very form.”
There is an interesting insight in this quotation. Ganesha is equated with mantra to the extent that mantra is his form. Mantras are used to remove obstacles; obstacles to knowledge, to success, to..anything! So as Vigneshwara, the Lord of Obstacles, mantras are by their very definition a manifestation of Ganesha.