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. No microphone needed — Key Detector analyzes your tab's audio directly, 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 IN v1.5 — Interactive Piano Keyboard The most-requested feature is here: a full C4–C5 interactive piano keyboard built right into the extension. Select any root note (C through B) and scale type (Chromatic, Major, or Minor) — the keyboard highlights which notes belong to that scale. When you run a key detection, the piano auto-syncs to the detected key and mode, so you can immediately see and hear the scale you're working with. Perfect for music theory practice, ear training, and finding the right notes to play along. 🔍 KEY DETECTION — VERDICT 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 with probability percentages • BPM tempo detection included • Results saved to session history 🎹 INTERACTIVE PIANO KEYBOARD (NEW in v1.5) • 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 Verdict results — no manual input needed ⚡ REAL-TIME 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 Verdict analysis. 🎛️ STUDIO MODE — PITCH TRANSPOSER (Pro) Transpose YouTube videos up or down by any number of semitones — in real-time, without affecting playback speed. 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 📋 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. The Krumhansl-Schmuckler algorithm computes pitch class profiles across the audio and correlates them against all 24 major/minor key templates to find the best match. BPM is detected via spectral flux analysis. The interactive piano uses Web Audio oscillator synthesis for note playback. Everything runs locally in your browser. 🔒 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 click Start. We collect no personal data. FREE vs PRO Free: • Key detection (Verdict Mode) • BPM detection • Real-time detection mode • Interactive piano keyboard (C4–C5, root + scale selector) • Session history (last 5 results) Pro (one-time purchase): • Studio Mode — real-time pitch transposer for YouTube • 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. 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. 🎵