SounID

I got in touch with the people from Sound ID. Here's what they said: "Sadly, Deezer does not support SoundID. To explain a bit further why a specific music app might not support SoundID, if the audio stream from the music app you're using can be shared with Android Services (Android EQ), then SoundID is able to see the audio stream and you will have the calibrated sound, otherwise, the music apps may not show/share the audio stream and there's no way for the SoundID app to know if you're playing some audio.

Currently, we are looking into potential solutions to widen the audience and provide a more seamless experience for our users. One of the solutions would be systemwide calibration, however, this will require root access and integration. We are working on further improvements and I can recommend staying in tune for future updates. We also recommend forwarding your feedback to the music app's developers for further consideration."

So, yeah, I smell an opportunity here...