Exporting audio only from iMovie

I'm looking for tips for exporting audio tracks only, from a movie clip with audio track, in iMovie. I will answer two ways below, which hopefully others can expand on.

Rant: Please, Apple, find another way to organise your community. Keep threads open and don't close them from lack of replies. Every time I come here I have to scroll through hundreds or thousands of matches to my searches, which I just don't have the time for. Who does? Do you? Other internet communities (especially the Stack Exchange ones) keep their questions together by having rules about not repeating questions, so you can search a topic and find all the accumulated answers in on place. Please!!!!