Question 1

How does the key finder work?

Accepted Answer

It detects the pitched notes in the first 30 seconds of your recording, builds a histogram of which pitch classes dominate — weighted by how long and how hard each note is held — and matches that against the profiles of all 24 major and minor keys. The best match is the answer you see.

Question 2

Does it work on a full song with vocals and drums?

Accepted Answer

It works, but less reliably than on a solo instrument. The detector listens for pitched notes and vocals, guitars and synths all count — which usually still points at the right key, but a busy mix lowers the confidence. When the margin between the best and second-best key is thin, the result says so.

Question 3

What's the difference between the key and the relative major/minor?

Accepted Answer

Relative keys — like C major and A minor — share the same key signature and nearly the same notes, so they're the classic ambiguity for any automatic key finder. When a song could honestly be either, we mark the answer low-confidence rather than pretend.

Question 4

Does it analyse the whole song?

Accepted Answer

It analyses the first 30 seconds of music, after any leading silence. For most songs that's plenty — keys rarely change that early. If your song modulates mid-way, the answer reflects the opening key.

Question 5

Is it free? Do you keep my file?

Accepted Answer

Free, and nothing is kept because nothing is sent — the audio is decoded and analysed entirely in your browser, on your device. Close the tab and it's gone.

What key is
this song in?

Questions, answered

Knowing the key is step one. Get the notes.

What key isthis song in?