Well it's you a person who is recording the music. So it's the user's responsibility to make sure you are not breaking any laws. So the app cannot be held at fault for this. No one cares if you do a Shazam in public so it all just works out.

But if you set up an autonomous recording device, no matter what you say you are doing, you will have problems.

Shazam is not illegal in Germany unless I missremember what the app does and instead of being to identify songs based on samples, it's being used to record people