The easiest way to figure out the key of a song is by using its key signature. The number of sharps/flats in the key signature tell you the key of the song. A key signature with no sharps or flats is the key of C (or A minor).
What is the easiest way to identify a key signature?
To find the name of a key signature with sharps, look at the sharp farthest to the right. The key signature is the note a half step above that last sharp. Key signatures can specify major or minor keys. To determine the name of a minor key, find the name of the key in major and then count backwards three half steps.
Is there an app to identify keys?
Once you have purchased your Tile, simply attach your Tile Mate key tracker to your keys and download the Tile app to your Apple iOS or Android device. If you lose your keys, open your Tile app and click on the keys icon.