If you self-hosted on WordPress then you could put a delay link at the end of each recording page to go to the next one – but that doesn’t stop people like me leaving the tab open until the link appears – there are some more complicated options that would force the tab to be the focus but that’s awkward with audio as you may well be taking notes, etc while it’s playing.
Or you could use a quiz style plugin to reveal the link. But that’s high hassle for a freebie and even for a paid-for course.
Drip feed by auto-responder is a reasonable compromise and one that works without any intervention on your part or the user once it’s set up. For a freebie, that’s OK in my view. One recording a day for X days with a reason to click & listen.
If it was me, I’d either do a single download page with links to each of the audios (uploaded in WordPress and then edited to open in a new window) or, if I was feeling keen, load them into a daily drip autoresponder.