There are several tools available online and as mobile apps that can help you find the key of a song. Here are some options:

1. Tunebat: This website has a database of over 70 million tracks and provides key and BPM information for any song.

2. Name That Key: This website allows you to identify the key of a song by inputting its chords. It searches all 12 possible keys for the selected chords and returns the keys with the most matches.

3. TuneBat Analyzer: This website allows you to upload your audio files to find the key and tempo of the tracks in your library. It is a tool for DJs interested in harmonic mixing, producers looking to remix songs, and anyone trying to understand their music a little better.

4. GetSongKEY: This website has a song analyzer that will find the key of a song, find the pitch of a song, song scale, or anything you want. It can analyze any audio like mp3 songs.

5. Song Key Finder: This mobile app for Android devices can analyze live music, local MP3s, or a set of chords to find the music key. All analysis is performed locally on the device, so it doesnt use your mobile data allowance.

6. Song Key Finder: This mobile app for iOS devices can identify the key of a song via several methods, including analyzing live music via the devices microphone, analyzing a local audio file on the device, or a set of user-entered chords. All analysis is performed locally on the device, so it doesnt use your mobile data allowance.

To find the key of a specific song, you can use any of these tools by inputting the songs title or uploading the audio file.