How to find a song's BPM and key (and mix with the Camelot wheel)

Knowing a song's tempo and key is useful for much more than DJing: picking songs that fit a workout, practicing an instrument with a metronome, making a remix or knowing whether you can sing it comfortably. You used to count beats against a clock and pick out notes on a piano; now an automatic analysis gives you both in seconds.

What BPM is

BPM stands for beats per minute. A song at 120 BPM has 120 beats every minute, two per second. It's the measure of tempo, and almost all popular music falls between 70 and 180 BPM.

How to work it out by hand

To check it without tools, count the kick drums or claps for 15 seconds and multiply by four. If you count 30, the song is around 120 BPM. It's a rough method, since missing or adding one beat shifts the result by four BPM, but it tells you whether the automatic analysis is in the right range.

Why you sometimes get double or half

It's the most common error of any tempo detector, and there's a musical reason: a song at 70 BPM with the drums playing eighth notes can easily feel like 140. Both readings are 'right' depending on where you place the beat. To settle it, tap TAP along with the rhythm as you'd tap your foot: the tool tells you whether you're at double, half or matching what it detected.

What the key is

The key is the set of notes a song is built on, with a central note that sounds like 'home'. There are 24: twelve major keys, which tend to sound bright, and twelve minor keys, darker or more melancholic. Each major key has a 'relative' minor that shares exactly the same notes: C major and A minor, for example.

The Camelot wheel, explained

To mix two songs without them clashing, they need to be in compatible keys. The Camelot wheel translates the 24 keys into a number from 1 to 12 and a letter: A for minor keys and B for major. That way you don't need any music theory:

• Same code (8A → 8A): same key. The safest mix.
• One number up or down (8A → 9A or 7A): a smooth change. Going up a number usually adds a bit of energy.
• Same number, other letter (8A → 8B): from minor to its relative major. It changes the color without clashing.

What to do with this data

• Match tempos: if two songs you want to blend are at 124 and 128 BPM, adjust one with the tempo changer, which changes speed without touching the pitch.
• Change key: if you want two songs to fit harmonically, or to sing one lower, use the pitch shifter, which transposes in semitones without changing the speed.
• Practice an instrument: drop the tempo to 75% to work on a hard passage and raise it gradually.
• Make your own beats: set the drum machine to the same BPM to play along with a song.

When the analysis fails

Detection is very reliable with music that has a strong beat: electronic, pop, rock or hip-hop. It's less exact with songs that change tempo, free passages without drums or very sparse arrangements. The key can also hesitate between a major and its relative minor, because they share notes; in that case the Camelot number is the same and the mix will still work.

FAQ

Is the song uploaded to a server?

No. The analysis runs in your browser and the file never leaves your device.

Does the pitch change if I change the tempo?

With the tempo changer, no. If you want both to change together, like on a turntable, try Nightcore to speed up or Nightcore Reverse to slow down.