BPM & Key Finder: Find the Tempo and Key of a Song

How to find the BPM and key of a song

1. Drop an mp3, wav, flac, m4a, or mp4 onto the page. It runs in your browser, and your song isn't uploaded.
2. Wait for the tempo and key to appear. If either one is uncertain, the page says so instead of guessing.
3. Clap or tap along. If your pulse is half or twice the number shown, read the section on double time below.
4. If the song changes tempo, loop a steady section and judge the click there.

How the tempo is worked out

The BPM finder listens for sharp, repeating attacks, such as kicks, snares, and strummed chords, and picks the tempo that lines up best with them across the whole file. It's an estimate from the audio you open, not a number looked up from a database, so it works on your own demos and rehearsal recordings as well as on released songs.

You get one number for the file. On a song recorded to a click, that number is usually right. On a live recording that drifts, it's a compromise between the slow verse and the fast chorus.

Double time and half time

This is the most common surprise. A ballad you feel at 70 BPM can read as 140, because the estimate locked onto eighth-note hi-hats. A half-time chorus can do the opposite. Neither reading is wrong, exactly: they describe the same grid at different levels.

The quick check is to tap the snare. In most pop and rock, the snare lands on beats 2 and 4. If tapping the snare gives you half the number on the screen, you're counting half notes and the display is counting quarters. Use whichever number matches how the band would count the song in.

How the key is worked out

The key finder measures how much of each of the twelve notes is in the mix and for how long, then picks the major or minor key that fits that profile best. It shows a single key.

Relative keys trip it up the most. C major and A minor use the same notes, so a song can come back as either. If the page says C major but the song feels sad, or the first chord you hear is A minor, trust your ear and call it A minor. Modes aren't labelled: a dorian tune will usually show up as a nearby major or minor key. A song that modulates for the last chorus gets one reading for the whole file.

What to do with the numbers

Two details people miss. The key shown describes the file as you opened it. If you transpose the player up two semitones, add two semitones to the key yourself. The BPM is also the original tempo. Slowing playback for practice doesn't change the number, which is what you want when you set a click.

• Set a metronome. Use the tempo to practice a part at the record's speed, or to set the click for a cover.
• Write a chart. The key tells you which signature to start from. Check the first and last chords by ear before you commit.
• Pick a key for a singer. If the original key is too high, the change key of a song page moves it in semitones without changing the speed.
• Make a backing track. If you want to play along without one of the parts, the stem splitter separates the song into six stems, and the drum remover makes a drumless version that uses the same tempo for its count-in.
• See the changes. The chord finder lays names along the waveform from the same mix, before any split. Treat them as a first draft and check the root by ear.

When the reading is unclear

Spoken word, ambient pieces, free-time intros, and very short clips often come back as unclear. That is deliberate: an honest "not sure" is more useful than a confident wrong number. Loop a section with a steady beat and a clear chord, and count it yourself.