How To Find The Key Of A Song

If you’re familiar with classical music, you’ve probably noticed stuff like “in D minor” in the pieces’ titles. It’s different with modern musicians, though — they don’t put out songs titled like “Star Shopping in Bm” on streaming platforms. How do you know what key a song is in and impress your friends or social media followers with an accurate cover version? Let’s learn together.

What is the key of a song?

Imagine that you went for a walk in the nearby park, then you went to a convenience store on the way home to buy groceries and finally returned to your place. Now imagine that you moved to a different city where your evening routine remained the same. However, you’d go to a different park, a different convenience store, and return to your new home. Functionally, the route is the same. It has a place for buying groceries, a place for birdwatching, and a place where you cook dinner and sleep. But the places themselves are different.

The key of a song, in this case, is the city — it defines where the “home” of your melody is and what “places” look like. Specifically, the “home” of any melody is the tonic. That’s why the key names in classical pieces’ titles like “Toccata and Fugue in D minor” contain the note’s “address” in the letter notation system. In this case, it means that D is the first note of the scale and the “home” to our melody — the place where it will always return. And the “minor” represents “the park,” “the convenience store,” and all the places your melody can go to — it describes what the rest of the scale looks like.

Why do you need to know the key of the song?

It’s like asking “why you need to know your home address” or “why you need a map” — so you don’t get lost in the sea of sounds. But if you want a serious answer, here’s why you need to know how to tell the key of a song:

You’ll come up with the best way to perform it. It’s not that relevant for pianists or singers. However, figuring out the key of a song is crucial for the instruments that depend on hand positions and fingering — from guitar to clarinet. For example, guitar players may need a capo for trickier keys so their hands don’t end up like this:

Four pictures of guitar frets with fingers in freaky and almost impossible positions — Source: Reddit

In this case, if you know how to tell what key a song is in guitar, you’ll be able to figure out the most comfortable fingering for each chord and learn if you need to help yourself with a capo.

You’ll get a starting point to move from. Imagine that you really liked a song and wanted to sing it, but once you started practicing, you discovered that it was way out of your vocal range. If you know the original key, you can transpose the backing track using software — and sing to it beautifully and freely, with no strain on your vocal cords.
You’ll respect the original idea. Although the concept of different keys carrying meanings is outdated, composers and songwriters don’t just randomly choose a key for a song — it’s an integral part of the music, and it creates a certain mood. So, if you want to keep this mood in your cover version, you need to know how to tell the key of a song.

What determines the key of a song?

If you have sheet music on your hands, it’s easy to figure out the key of a song — take a look at the signatures:

The sheet music of the Main Titles theme from “The Split” with key signatures highlighted in red — Source: Evan Jolly

The flat sign means that the note should be a half-step lower — as opposed to the sharp sign, which means that the note should be a half-step higher. In this case, the key signatures mean that B, E, and A are half-step lower by default, which corresponds with E flat major or C minor. Here’s the full spreadsheet with key signatures for different keys that will help you learn how to tell what key a song is in piano:

Sharps		Flats
C major/A minor		No sharps or flats
G major/E minor	1	F major/D minor	1
D major/B minor	2	B♭ major/G minor	2
A major/F# minor	3	E♭ major/C minor	3
E major/C# minor	4	A♭ major/F minor	4
B major/G# minor	5	D♭ major/B♭ minor	5
F# major/D# minor	6	G♭ major/E♭ minor	6
C# major/A# minor	7	C♭ major/A♭ minor	7

How to tell what key a song is in using software

What if you can’t find sheet music, or the sheet music you found is inaccurate or transposed? Luckily, machines can answer the question “What key is this song in?” for you — let’s do a quick tour and explore the world of key analysis software.

DJ software

Traktor, Serato, Rekordbox, and other apps for mixing and recording DJ sets — all of them have a native key analysis feature. DJs need this data for harmonic mixing, which means taking not only BPMs but also harmonies and melodies into account for a more cohesive sound. And, while key analysis in DJ software can be somewhat helpful for the DJs who can’t find song keys by ear, it’s not 100% accurate.

Playlist in Traktor Pro 3 with analyzed keys in the Camelot system — Source: macProVideo.com

The default key format in Traktor Pro 3 also looks like this. Yep, these are keys, according to the Camelot system — which may come off as very confusing for people with formal music training.

All the programs we mentioned determine the key of a song using statistics — they compare the notes most common in certain keys and the notes most common in a particular song. They can also use the first note or the first chord as the root note. The problem is music is not that formulaic! For example, the song We No Who U R by Nick Cave & The Bad Seeds is all in A minor with no modulations, and it starts with the tonic chord. But this song by TR/ST changes the key halfway through. And this song by Grimes starts with an A♭ major chord, even though its actual key is C minor. Key analysis in DJ software will probably make a mistake in these two cases.

The takeaway is: trust Traktor or whatever app you use for DJing with a huge grain of salt — just because the app figured out the key for you doesn’t mean you shouldn’t listen and double-check.

Key analyzing software

How to know what key a song is in if you don’t DJ? Apps like Traktor and Rekordbox are too heavy and convoluted to use just for key analysis, right? Luckily, there are a lot of key analyzing resources out there. We won’t list all of them, but here are some of the most prominent:

Mixed in Key. This app analyzes tracks for harmonic mixing. According to a study conducted by a Reddit user in 2021, it’s the most accurate key detection tool compared to human ears, defining keys correctly in 84.9% of cases.
KeyFinder. This old tool for key detection is very straightforward and minimalist — you upload tracks, press “Run batch analysis”, and wait for a while. The only problem with this app is that it hasn’t been updated since the 2010s.
Song Key & BPM Finder. If you don’t want to spend time installing stuff on your computer, try online resources. This website analyzes keys and BPMs of your uploaded files, and the best part is that it displays keys both in the Camelot system and the regular way.
Tunebat. It’s an online database of songs with keys, BPMs, and even suggestions for mixing — unless your song of choice is very obscure, you can just search it on the website. And if it is obscure, upload your file on Tunebat’s key analyzer. The problem with the database, though, is that the key data is taken from DJ software — and, as we mentioned, it’s not always accurate.

AI-powered key analyzing software

Artificial intelligence doesn’t just judge your music taste — it can also be a helpful tool for musicians. Let’s take a look at what the AI market offers for key detection:

Moises.ai. This tool offers instrumental splitting, key detection and transposition, and it even finds chord progressions for you. The best part is that it has an iOS app, so you can find keys for all the songs you need on the go.
Key Detector. This paid plugin by Waves detects keys and scales in separate tracks and full instrumentals. It can even transpose the tracks that are offkey so they fit in the rest of the instrumental. Unfortunately, it has no free trial.
Voice.ai. This tool, unlike Moises and Key Detector, is free and doesn’t require signing up. However, the legitimacy of its key and BPM detection tool is questionable. For example, this output for John Coltrane’s (in)famous jazz classic couldn’t be further from the truth.

Voice.ai key and BPM finder providing inaccurate results (93 BPM and C minor) for John Coltrane’s Giant Steps

Wrapping up

The concept of key is actually a lot more complex than we explained earlier, and it will always remain a topic for heated discussions about music theory. That’s why even the most precise key detection tools fail to identify keys 100% correctly, especially for complex tunes. While you can use them for simpler cases or opt for the most precise tool on the market, we still suggest that the best key detection software is your ear — or your friend with perfect pitch.