Key and BPM finder
Drop in a track and get its tempo, musical key and Camelot code — plus energy, loudness and a full mix profile — read by the same analysis engine that tags every track on Postal, not a quick in-browser estimate.
Drop an audio file here, or click to browseMP3, WAV, M4A, FLAC or OGG — up to 80 MB
Analyzed on our servers by the same engine that powers Postal, then discarded — your file is never stored.
What each reading means
124
BPM
Beats per minute, from a beat tracker that follows the low-frequency pulse of the whole track. Steady electronic and pop material usually lands within a decimal place; rubato or beatless material has no single true answer.
A min
Key
The tonal centre and mode, from the track's pitch-class distribution measured against major and minor key profiles. Reported as one key for the whole track — songs that modulate get the key that dominates.
8A
Camelot
The DJ-wheel position of the key. Adjacent numbers and same-number letter swaps mix harmonically: from 8A, try 7A, 9A or 8B. Minor keys are A, major keys are B.
High
Confidence
How strongly the evidence agrees. BPM confidence comes from beat-grid stability and agreement between tempo estimates; key confidence is the strength of the winning profile match. Low confidence means listen and judge for yourself.
72/100
Energy
A composite intensity score blending how loud the master is, how many musical events land per second, how much high-frequency content it carries, and how fast it moves. Useful for sequencing a set or a playlist by feel.
-9.2 LUFS
Loudness
Integrated loudness to the broadcast standard (EBU R128), with true peak and loudness range. Streaming platforms normalise to around -14 LUFS, so a hotter master gets turned down — the reading tells you by how much.
Sub·Low·Mid·High
Mix profile
Where the energy sits across the frequency spectrum, plus stereo width and mono compatibility. A quick sanity check that the low end, brightness and stereo image of a bounce came out the way you meant.
▁▃▆█▆▃
Energy timeline
The track's loudness over time, normalised to its own peak — drops, breakdowns and outros read at a glance, so you can see the arrangement's shape before you even hit play.
Analyzed by a production engine, not a widget
Every track uploaded to Postal is analyzed for tempo, key, loudness and dozens of other features so producers can search and sort a real catalogue by them. That analysis has to be right at scale — it is evaluated against a labelled corpus and tuned where generic extractors fall short, including a key detector built in-house.
This page is a direct line into that same service. The file you drop here goes through the identical decode, beat tracking and key detection code path a Postal upload does, and the result you see is the result the product would store. When the tool and the platform agree with themselves, you can actually compare numbers across your library.
What no analyzer can do is out-hear you. A track that changes tempo, drifts, or sits between two keys gets one answer with a confidence attached — treat a low-confidence reading as a prompt to check by ear, not as a verdict.
Frequently asked questions
Most free tools decode a slice of the file in your browser with a generic beat tracker. This page runs your audio through the same analysis service Postal uses in production — the identical tempo tracker and key detector that tag every track uploaded to the platform, tuned and evaluated against a labelled corpus. You get the number the actual product would store, not an approximation of it.
The file is sent to our analysis server over HTTPS, decoded in a temporary file, analyzed, and deleted when the request finishes. It is not stored, added to any library, or used for anything beyond returning your result.
Beat trackers work inside a 60–180 BPM window, so genres that live outside it get folded one octave in: a 170 BPM drum & bass track can read as 85, a 70 BPM ballad as 140. Musically both answers describe the same pulse — use the ½× and 2× buttons to see the tempo the way you count it.
Key detection compares the track's overall pitch content against major and minor profiles, and different tools use different profiles and weightings — near-ties between relative keys (A minor vs C major) are common, and heavily effected or modulating tracks can genuinely be read more than one way. The confidence badge tells you how decisive the match was.
A renaming of the circle of fifths for DJs: 12 positions, each with an A (minor) and B (major) side. Keys that are one step apart on the wheel, or share a number across the A/B sides, are harmonically compatible — so 8A mixes cleanly with 7A, 9A and 8B. It exists so you can match keys without thinking about music theory mid-set.
It is a documented heuristic over measured signals, not a black box: integrated loudness carries the most weight, blended with onset density (how many note and drum events land per second), spectral brightness, and tempo. Each is measured by the same production analysis code Postal uses — the blend just turns four honest numbers into one you can sort by.
LUFS is the broadcast-standard loudness measurement (EBU R128) — how loud the track is overall, perceptually weighted. Most streaming platforms normalise playback to around -14 LUFS, so mastering hotter than that buys no loudness on Spotify, it just costs dynamics. True peak is the highest instantaneous level (keep it under -1 dBTP to survive lossy encoding without clipping), and loudness range (LU) measures how much the loudness varies — low values read as compressed, high values as dynamic.
Clubs, phones and many Bluetooth speakers sum stereo to mono. If parts of your mix are out of phase between left and right, they cancel when summed and disappear. The score is derived from the phase correlation between channels — near 100% means the mix survives mono; a low score means check what vanishes when you press the mono button.
MP3, WAV, M4A/AAC, FLAC, OGG and AIFF, up to 80 MB. The whole file is decoded and analyzed — not just a slice from the middle — so longer tracks simply take a moment more.
Key and BPM on every track, automatically
Upload your library to Postal and every track gets tempo, key and deeper analysis the moment it lands — searchable, sortable and always with the file.
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