Ah, you're behind the times. You may be remembering 2008 when Amazon had those big "DRM Free" messages and t-shirts and talked a lot about how music wanted to be free. It was a big part of their sales pitch. That faded away, and then some music started using DRM. However, if you purchase a music song or album, you can still mostly download MP3s, as far as I know.

On the other hand, if you use Amazon Unlimited or Amazon Music Prime, you cannot download music as MP3s. You need to use a player that supports their DRM.

That's still there although they emphasise it less and less (they want you on the monthly "unlimited" subscription instead). But only for music; their video offering is locked streams only, for example.

Does anybody know how to do this? I'm trying to download some albums I bought back in 2010, but I can't see anywhere to download the MP3s. It will only let me play it through the web player.