The tuner has got different modes. One of it is the pitch pipe. To switch between tuner and pitch pipe, use the ‘Mode’ button in the left corner.

The tuner is always in chromatic mode. So you can tune every other instrument like a zither, a Chapman Stick, a autoharp or piano.

Sometimes another app is using the microphone and blocks the access to the microphone for other apps. Please close this app or if it is not clear which app blocks the microphone, close them all. If this does not help, reboot your phone.

In rare cases it has to do with the permissions. The ‘audio record’ permission is needed for the tuner. Maybe the permission has been revoked. There is
the possibility to withdraw permissions with Android 6 or higher. Please check: ‘Info’ -> ‘Permissions’ -> ‘Permissions’

The screen overlay is originally a problem of Android 6. And it happens, if an app requests a permission. The tuner e.g. needs the audio permission.

The reason for this message:
This message appears when you’re running a floating app, and then start a newly installed one, which requests access rights. Floating apps include the chat heads of Facebook Messenger that can appear floating above other. One solution is to grand the permission before opening the tuner. Please go to ‘Info -> Permissions -> Permissions’ and grand the audio permission to smartChord.