Key Detector – Musical Key & BPM Finder

Detect the musical key & BPM of any audio in your browser. Transpose YouTube in real-time. Interactive piano keyboard included.

🎵 KEY DETECTOR & TRANSPOSER — Musical Key Finder, BPM Detector & YouTube Pitch Transposer Instantly find the musical key and BPM of any song playing in your browser tab — or upload an audio file directly for offline analysis. No microphone needed. Key Detector analyzes audio using professional-grade signal processing to identify key, mode, and tempo in seconds. Used by guitarists, singers, producers, music students, and transcribers to answer the #1 question: "What key is this song in?" ★ WHAT'S NEW • Analyze audio files directly — upload an MP3, WAV, FLAC, OGG, or M4A file and get an instant key & BPM result without playing it in a tab. Free users get 1 analysis per week; Pro users get unlimited. • Improved BPM accuracy — rewritten tempo engine with harmonic comb filtering, perceptual preference, and sub-sample interpolation for more reliable results across a wide range of music styles. • Cleaner Studio Mode — Speed control is now a Pro feature like Transpose, with a consistent lock interface. No confusing mixed states. • Clickable logo — opens keydetector.site for tips, changelog, and updates. 🔍 KEY DETECTION — DETECT MODE Analyzes 15–60 seconds of audio for maximum accuracy. Uses the Krumhansl-Schmuckler key-finding algorithm — the same method used in professional music analysis software — to detect all 24 major and minor keys. • Detects key and mode (major or minor) with confidence score • Color-coded confidence: green (high), amber (medium), red (low) • Shows top 3 alternative key candidates • BPM tempo detection included • Manual Tap BPM tool — tap along to find the tempo by hand • Results saved to session history 📁 AUDIO FILE ANALYSIS Don't have the song open in a tab? Upload the file instead. Drag and drop or browse for any MP3, WAV, FLAC, OGG, or M4A file and Key Detector will analyze it offline — no tab capture needed, no audio playing required. Great for analyzing your own recordings, downloaded tracks, or samples. • Supports MP3, WAV, FLAC, OGG, M4A • Same Krumhansl-Schmuckler key detection as live mode • BPM detection included • Results appear in the Detect tab and are saved to history (marked with 📁) • Free: 3 analyses per week — Pro: unlimited 🎹 INTERACTIVE PIANO KEYBOARD • C4–C5 range with accurate black and white key layout • Highlights root note and in-scale tones for any key • Manual root selector (C, C♯, D, D♯, E, F, F♯, G, G♯, A, A♯, B) • Scale selector: Chromatic, Major, Minor • Click any key to hear the note (built-in audio synthesis) • Auto-syncs with Detect results — no manual input needed ⚡ LIVE KEY DETECTION Continuous detection mode that updates every few seconds as the audio plays. Great for tracking modulations in longer tracks or getting a quick read before committing to a full Detect analysis. 🎛️ STUDIO MODE — PITCH TRANSPOSER & SPEED CONTROL (Pro) Transpose YouTube videos up or down by any number of semitones — in real-time, without affecting playback speed. Also adjust playback speed independently. Powered by SoundTouch audio processing. Ideal for: • Singers who want to perform a song in a more comfortable key • Guitarists who want to play along without retuning • Producers matching the key of a sample to their project • Language learners who need audio slowed down 📋 SESSION HISTORY Every key and BPM detection is logged automatically. Review your recent analyses, compare results across songs, and pick up where you left off. WHO IS KEY DETECTOR FOR? ✓ Guitarists & instrumentalists — find the key of any song to jam along ✓ Singers & vocalists — detect key before performing, transpose to your range with Studio Mode ✓ Music producers & DJs — confirm key and BPM for harmonic mixing and mashups ✓ Music students — visualize scales on the piano keyboard, practice ear training ✓ Transcribers & arrangers — identify key signatures in seconds, not minutes ✓ Karaoke singers — transpose YouTube songs to match your voice ✓ Songwriters — quickly identify the key of a reference track HOW IT WORKS (Technical) Key Detector uses the Web Audio API to capture your tab's audio stream in real time. For file analysis, it decodes the file locally using the browser's built-in audio decoder. The Krumhansl-Schmuckler algorithm computes pitch class profiles and correlates them against all 24 major/minor key templates to find the best match. BPM is detected via spectral flux analysis with harmonic comb filtering. The interactive piano uses Web Audio oscillator synthesis for note playback. Everything runs locally in your browser — no servers involved. 🔒 PRIVACY — 100% LOCAL PROCESSING Your audio never leaves your device. Key Detector processes everything directly in the browser — no audio is uploaded, recorded, or stored on any server. Detection only runs when you actively start it. We collect no personal data. FREE vs PRO Free: • Key detection (Detect mode) • BPM detection + manual Tap BPM tool • Live (real-time) detection mode • Audio file analysis (3 files per week) • Interactive piano keyboard (C4–C5, root + scale selector) • Session history (last 5 results) Pro (one-time purchase): • Studio Mode — real-time pitch transposer + speed control for YouTube • Unlimited audio file analysis • Camelot wheel — DJ & harmonic-mixing notation • Dark mode • Extended session history • Early access to new features SUPPORTED SITES Works on YouTube, SoundCloud, Spotify Web, Bandcamp, and virtually any website that plays audio in a browser tab. File analysis works with any locally stored audio file. If Key Detector helped you find the key of a song you've been searching for, please take a moment to leave a review — it helps other musicians discover this tool. 🎵