Play or sing a song and reveal its key — for covers, transposing & harmonic mixing.
Start, then play or sing a verse/chorus for 10–30 seconds. We build a pitch-class profile and match it against all 24 keys — handy for transposing a cover or beat-matching by key.
A song's key is defined by which notes it uses most. As you play, this key finder counts how often each of the 12 pitch classes (C, C#, D … B) appears, building a pitch-class histogram. It then correlates that profile against the 24 major and minor key profiles using the Krumhansl-Schmuckler algorithm — the same tonal-analysis method used in music information retrieval.
Because relative major and minor keys share the exact same notes (for example C major and A minor), the tool shows the best match plus the closest runner-up. Trust your ear: the key that feels like "home" at the end of a phrase is usually the right one.
Play a section with a clear melody or chord progression — a verse or chorus works better than a single held note. Keep background noise low and let the detector collect at least 10 seconds of audio. If the result looks unstable, reset and try a different section of the song. For best results, play along with the actual track rather than humming a single line.
A song key finder answers a question your ear can feel but not always name: "what key is this in?" It does so by counting. As you play, it tallies how often each of the twelve pitch classes appears, building a histogram of the song. It then compares that profile against the twenty-four major and minor key profiles from the Krumhansl-Schmuckler study, a well-known model of how strongly each note belongs in each key. The key whose profile best matches your song's histogram wins, and the runner-up is shown too. That is real music-information retrieval running on a single page.
The method is statistical, not absolute. A song that leans on the tonic and dominant will match its key cleanly; a song that wanders through modes or uses blue notes may show a weaker, more ambiguous result. The key finder reports a match strength so you can see how confident the reading is, rather than pretending every guess is certain.
The most common surprise a key finder delivers is showing two keys. That happens because relative major and minor share the exact same notes — C major and A minor use the identical seven letters, so a pitch-class histogram cannot tell them apart on its own. The finder shows the best match and the closest alternative, and your ear breaks the tie: the note that feels like "home" at the end of a phrase is the true key. Knowing this saves players from arguing with the tool when it "switches" between C and Am.
Once a key finder names the key, everything gets easier. Singers transpose a cover up or down to fit their range; guitarists pick chords that belong to that key instead of guessing; producers check whether a sample will clash. DJs use key results to beat-match by musical compatibility, not just tempo, so transitions sound smooth instead of sour. The key finder turns a vague "this song feels like it's in G" into a definite "G major," and that certainty is what lets you act on it.
A key finder is a helper, not an oracle. It needs enough notes to build a reliable profile, so a single held chord or a ten-second snippet may mislead it; play a full verse or chorus for the best result. Modal tunes, heavy chromaticism, and songs that change key midway can confuse the statistics. When the result looks wrong, trust the musician in the loop: reset, try a different section, and let your ear confirm what the algorithm only estimates. The key finder is fastest when you and it agree.
A key finder is only worth running if you act on what it shows. Once it names the key, write it down before you forget, then use it: transpose a tricky vocal line, choose chords that belong to that key, or check a second instrument is in the same key before you record. The key finder gives you the answer in seconds; the musician turns that answer into a better performance. When the result looks shaky, play a longer section and let the key finder build a fuller picture rather than trusting a thin snippet — the extra seconds almost always clarify the key. Treat the key finder as the first step of arranging, not a party trick, and it will save you from the classic mistake of writing a harmony in the wrong key.
A song key finder listens to the notes you play or sing, builds a pitch-class profile, and compares it against the 24 major and minor keys to tell you which key the song is most likely in.
Yes, 100% free forever — no sign-up, no download. Everything runs in your browser.
It uses the Krumhansl-Schmuckler algorithm: it counts how often each of the 12 pitch classes appears and correlates that profile with the standard major and minor key profiles.
Yes, any modern browser on phone, tablet, or desktop, including iOS and Android.
No. All audio processing happens locally in your browser. Nothing is ever uploaded.
Play or sing a clear verse or chorus for 10–30 seconds so the detector has enough notes to build a reliable profile.
Major keys and their relative minor share the same notes, so the result shows the best match plus a close runner-up. Use your ear to tell which feels like home.
Knowing a song's key unlocks everything: you can transpose it to fit your voice, find compatible chords for a cover, mix tracks in a DJ set, or write a harmony line. Our free online song key finder does this entirely in your browser with no upload and no account. It is perfect for singers covering a song, guitarists learning a track, producers checking a sample, and DJs beat-matching by key.
Because it is a true in-browser key detector, your audio never leaves the device — private by design. Combine it with our pitch detector to check individual notes or our online tuner to tune your instrument first.
Explore more tools from PitchTester