How to Determine the Key of a Song

You can determine the key of a song by analyzing its chords, humming a likely tonic and matching it on the piano, looking at the sharps and flats in the song’s sheet music, using key-finding software, or conducting a basic Google search. In some cases, you also need to identify major and minor scales.

Methods for identifying the key of a song

Many songs have a clear key, even if they feature non-diatonic chords that do not belong to its main scale. Others change key, use modes, or avoid a single tonal center. There are several ways of identifying a song’s key; regardless of your knowledge of music theory, I believe you’ll find at least one of the methods listed below suitable.

1. Analyzing the chords in the song

You do not need perfect pitch to hear which note or chord feels settled. If you know the chords of a song, you already have useful clues to its key. Start by analyzing the first, last, and most common chords in the progression, then listen for the chord that feels like a point of rest.

If you’re playing a song that starts with the chord G Major and in which G Major is the most-commonly featured chord, then there’s a very good chance that song is in the key of G Major. The same applies to a song that starts and ends with A Minor and in which A minor is heavily featured (in this case, the song’s probably in the key of A Minor).

Naturally, this is a rule of thumb, not a mathematical formula that applies to all songs. In some cases, you need to determine or “feel” which chord sounds most like “home.” In tonal music, the tonic chord often conveys a feeling of resolution after tension. When a chord creates a sensation of arrival, closure, or conclusion, it may be the tonic chord; the note naming that home key is the tonic.

2. Humming along to the song

You won’t always have access to the chords of a song. A good alternative is humming along to it. Try humming the note that feels like a resting point at the end of a phrase, then use a piano to identify the pitch. Check it against more than one phrase. A note that fits over one chord is not necessarily the tonic, and the tonic will not sound equally settled against every chord.

This method is easier than it seems, but it can be tricky for one reason: it starts with one note, rather than a complete chord or scale. After finding a likely tonic, you still need to work out whether the song is in a major or minor key, or uses another mode. I will explore this below. Mood can suggest a starting guess, but happy and sad are not reliable tests of major and minor.

Note: you can also try using a tuner app to see which note you’re humming. Naturally, many might have difficulty replicating the exact note sound, but it’s worth a shot.

3. Looking at the song’s sheet music

Some pieces of sheet music name the key in the title or other information; many expect you to read the notation. Start with the key signature, the group of sharps or flats near the clef at the beginning of a staff. Do not count every accidental beside a note. The treble and bass staves normally share the same key signature in piano music.

Sharps and flats raise or lower written notes by a semitone. Many correspond to black keys on the piano, but E-sharp and B-sharp, for example, are played on white keys. A key signature with no sharps or flats suggests C Major or A Minor in ordinary major/minor music; it does not by itself distinguish those keys or rule out modes and chromatic notes.

For a sharp key signature, identify the last sharp in the signature and go one half-step up to find the major key. If the last sharp is A#, the major candidate is B Major. For signatures with two or more flats, the second-to-last flat names the major candidate; one flat means F Major. Listen to the music to confirm which tonal center it uses.

It is important to know the relationship between major and minor scales. Relative major and minor keys share a key signature: the minor tonic is three half-steps below the major tonic. The signature ending in A# therefore suggests B Major or G# Minor, not C Minor. C Minor has three flats: B♭, E♭, and A♭. The distinction between sharp and flat note names matters when spelling a scale.

4. Using key-finding software

We’re lucky to live in a technological age in which many tools are available to help us find a song’s key. Using key-finding software is one of the easiest ways of determining the key of a song because it doesn’t require any knowledge of music theory, or even a trained ear.

There are many VSTs, websites, and apps to choose from, some of which are either free or very accessible. You can find useful options in this article.

5. Searching Google

If you’re trying to find a popular song’s key, searching Google can be a useful starting point. Write the artist and song title followed by “key,” then check that the result refers to the same recording or arrangement you are using. A live version, cover, or transposed chart may be in a different key.

While extremely convenient, this method will not solve all of your key-finding needs. A search may miss an unfamiliar song, repeat an incorrect analysis, or give one key for music that changes tonal center. Use the result as a clue and test it against the recording or score, especially when the suggested key does not sound right as you play along.

What is a song’s key?

A song’s key identifies a tonal center and its major or minor setting. The central note is called the tonic. “Root” usually refers to the note that names an individual chord, so the root changes as the chords change while the tonic may stay the same. Knowing the key helps you understand those relationships; it does not mean one note will fit every moment.

The Beatles’ hit song “Hey Jude,” for example, is in F Major. That gives you a useful starting point for improvising, but it does not guarantee every F Major scale note will suit every chord. Listen to the progression and phrasing as well. Knowing the key can also help you work out chords without immediately reaching for a chart.

Learning how to identify a song’s key is also great for composing. If you’re working with a basic motif and want to add some harmony to it, knowing the key that best suits the motif is the best way of coming up with a fitting chord progression on the spot.

Every music producer and instrumentist should know how to quickly identify a song’s key. Luckily, there are various methods for doing so.

How to distinguish between major and minor scales

While there are seven basic modes in western music, most songs tend to be composed either in the Major or Minor mode (which is the same as the Major and Minor scales). Learning how to distinguish between these two is the best way of correctly finding the key of a song after identifying its tonic.

Mood can suggest a first guess, but listening to the intervals and the tonic chord is more reliable. Major-key songs can sound sad, and minor-key songs can be lively. A useful way to test your guess is playing the third note of each candidate scale and listening to how it fits with the melody and home chord. Check more than one phrase, especially if the harmony changes.

Imagine that you’re trying to find the key of a song that’s neither too happy nor too sad and that’s centered around the note C. You just need to play the third note of the C Major scale (E) and see if it fits with the song. If it doesn’t, try the third note of the C Minor Scale (E♭) to see if it sounds any better. Listening to the major and minor thirds in the context of a song is perfect for telling major and minor scales apart.

Watch out for non-diatonic chords

In tonal music, a non-diatonic chord uses one or more notes outside the main diatonic scale of the key. A flat-six chord is one example, often borrowed from the parallel minor in a major-key song. It is not the only common option: secondary dominants and other borrowed chords also occur. You will hear chromatic harmony in many styles, including jazz, world music, and math rock.

The Beatles’ “I Saw Her Standing There” is centered on E, but the harmony at the falsetto “wooh” brings in C-natural, outside E Major. It can sound like a C Major flat-six chord; closer analysis hears A Minor over C in the bass, a borrowed minor-four chord. Either reading shows why one outside note need not mean a change of key. Do not let one outside chord decide the key for you. Listen for the larger pattern of departure and return, and check whether a new section actually establishes another tonal center.

Conclusion

I hope this guide to determining the key of a song will help you to play, jam, and compose more quickly and with better results. The five methods offer different clues, and it is useful to know them all. Compare those clues when a song changes key or the answer is unclear, rather than expecting one method to settle every case.