“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.”
-Natchintanai
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.