In addition to all the other great recommendations, and in part to expose the idea, if you want to go really low tech, there are a variety of phone apps that will record audio in .mp3 format. If you give it a flexible enough license, you can upload/host your audio with notes and other meta data for free on Archive.org
. (OER podcasting anyone?)
Then to quickly generate a subscribe-able podcast feed, create a free Huffduffer.com account (using the class name perhaps?) and use Huffduffer’s browser bookmarklet to save your Archive.org posts to your account. Huffduffer can provide podcast feeds out of individual user accounts, collectives, and even by tags, so you’ve got a lot of flexibility in how you and students can subscribe to content there. As an example you can subscribe to a “community podcast” for the tag A Domain of One’s Own.
If you create a custom/unique tag for the class, students can record and tag their own content to create an audio conversation back and forth if desired.