Key, BPM & Time Signature Detector

What Is the Key, BPM and Time Signature Detector?

The Key, BPM and Time Signature Detector is a free online music analyser that listens to a song and tells you its musical key, its tempo in beats per minute and its time signature in a few seconds. It works on any audio or video file, including MP3, WAV, FLAC, M4A, MP4, MOV, MKV and WEBM, and you can analyse up to 10 files at once and compare them in one table. Every result comes with a confidence score, a Camelot code for DJ mixing, a runner-up key and an alternative way to write the meter. It is made for musicians, producers, DJs, singers, music teachers and anyone who wants to find the key and BPM of a song before practising, remixing or mixing it. It works in four simple steps: upload your files, wait for the analysis, read the results, then sort or download them as an Excel file.

How to Find the Key and BPM of a Song: Step by Step

Step 1: Upload your files. Click Upload Audio or Video Files, or drag and drop files anywhere on the upload panel. You can add up to 10 files at a time and mix any formats, and you can press Add files later to continue the same table.

Step 2: Wait for the analysis. Each file is analysed in turn, and its row shows the current stage and a progress bar. Formats your browser cannot read directly are converted automatically first, which can take a little longer. You can remove a file at any moment with the cross button.

Step 3: Read the results. Every finished row shows the detected key with its Camelot code, the detected BPM and the time signature. Each value has a confidence ring: green means high (70% and above), orange means medium (40 to 69%) and red means low (below 40%). Hover over a value to see the runner-up key, the tuning offset or the alternative time signature.

Step 4: Sort the table. Use the Sort by menu to order the songs by name, detected key, detected BPM or time signature, and use the arrow button to reverse the order. On a desktop screen you can also click the column headings.

Step 5: Download or clear. Click Download Excel to save all results as an .xlsx file, or click Clear table to start a fresh batch.

Key Detection with Camelot Codes and Tuning Check

The key detector finds the tonic and the mode (major or minor) of a song and shows it with a Camelot wheel code such as 8A or 11B, so DJs can match tracks for harmonic mixing. It also shows the second most likely key, which helps when a song sits between a major key and its relative minor. The tool measures the true tuning of the recording in cents from A440, so songs that are slightly sharp or flat, such as old recordings or tracks with a pitch shift, are still read correctly. Use the confidence ring as a guide and confirm doubtful results by ear.

BPM and Tempo Detection

The BPM detector measures the tempo of the song and corrects the common half-time and double-time mistakes, so a slow song is not reported at twice its real speed. It follows the beat across the whole analysed section, so songs with a steady groove, electronic tracks and live band recordings all give a stable tempo value. The result is shown as a whole number with its own confidence ring, which is useful for DJ sets, practice with a metronome, video editing and syncing loops.

Time Signature Detection for Common and Odd Meters

The time signature detector finds how many beats are grouped in a bar and reports meters such as 4/4, 3/4, 6/8, 5/4 and 7/8. When two readings sound the same, for example 3/4 and 6/8, the tool shows the main result and lists the other way of writing it beside it, so you can choose the notation you prefer. Triple-feel songs such as waltzes are recognised, and unusual odd-time songs are reported with a lower confidence when the pattern is not clear.

Bulk Analysis, Supported Formats and File Conversion

The tool accepts almost every audio and video format, including MP3, WAV, FLAC, M4A, AAC, OGG, OPUS, AIFF, WMA, MP4, MOV, MKV, AVI, WEBM and many more, and it reads the sound track of a video file directly. Files that your browser cannot decode are converted automatically by a built-in converter, with no extra step for you. If a file type is not supported, or a file cannot be read, a clear message tells you which file was skipped and why. Up to 10 files can be added in one go, and the table keeps them together for easy comparison.

Long Songs and the Analysed Section

For tracks longer than 4 minutes, the detector analyses the middle 4:00 of the song, where the full arrangement is usually playing, and a notice tells you when this happens. The table shows the real duration of the file and the analysed section for each song, and both are included in the Excel export.

Export Results to Excel

The Excel download contains one row for each song with the file name, detected key, Camelot code, key confidence, runner-up key, detected BPM, BPM confidence, time signature, time signature confidence, alternative time signature, duration, analysed section, batch number and status. The rows follow the order you have chosen in the table, so you can sort first and then download.

Technical Details and Privacy

The detector runs entirely in your browser using digital signal processing, so your files are never uploaded to a server and no sign-up is needed. The audio is first reduced to a mono signal and then analysed with a fast Fourier transform. Tempo is found from spectral-flux onset detection, a Fourier tempogram and autocorrelation. The key is found from chroma (pitch-class) features, with a bass emphasis and tuning correction, and is matched against several established key profiles, including Krumhansl-Schmuckler and Temperley. The time signature comes from beat tracking and the bar-length pattern of accents and chord changes. For the best accuracy, use a clean, full-quality recording of the whole song.