You’ll need to tap the mic button and play your guitar close to your device after granting the tuner access to your device’s microphone. In some cases, you may even need to play your instrument loudly enough for it to register.
According to Android Police, the built-in tuner uses your device’s microphone to help you find the right tune for your instrument. To use the feature, simply search for “Google tuner” in Search, and the chromatic tuner will appear at the top of the results page. It’s available on mobile devices, including the best Android phones, as well as laptops.