We actually have a whole page on "Themes: Language," which is super important to the book. You know, there's a particular language that people use for magic (Old Hardic) and magic is only possible if you know the true names. Ged even thinks about himself as being a word spoken by the sunlight (3.13).
But there's something that doesn't entirely fit, which is that song and dance are particularly important in Earthsea's culture. All of their historical lessons are put into poems and songs (which the Master Chanter teaches the students). And one of the most important ceremonies of Earthsea is the Long Dance, which is their New Year's celebration – they sing all about the history and dance to welcome the new year (4.6-7). By singing and dancing all together, the people of Earthsea share a connection.
And on that note, check out this line: "So, as the mageborn will, Ged made his fear and regret into a song, a brief lament, halfsung, that was not for himself alone" (10.11). Interesting. It seems like speaking spells is a very individual thing to do; but by contrast, singing is a public and social act – it's a way to share.