According to this post:
third party apps will not any longer have access to streaming Spotify
content in a way that works for slowing down audio.
This will affect Amazing Slow Downer for iOS and Android starting September
We can now confirm that Spotify kept their
promise. The combination of Amazing Slow Downer and Spotify is now history.
It's very important that you as a user complain and ask that they reconsider
their decision. Spotify have forums for both regular users and developers.
This is a link to our post on their developer forum:
And this is the link to the entry point of their forums:
Official Spotify support on Facebook.
You can sign a petition here
Please raise your voice everywhere you can think of since that's the only way we can make Spotify change their mind!
This change does NOT affect any other type of audio content that Amazing Slow Downer can play back.