BeatLock: Metronome & Tempo

The metronome that clicks the instant you tap, and locks to the song you're playing along with.
Play a song, and in a few seconds BeatLock finds its tempo and beat, then takes over in time.
Nudge the beat earlier or later while it plays. The tempo stays put.

INSTANT START, NO DRIFT
The first click lands right away, with no wait for a full beat. Every beat is scheduled at an absolute time on the audio clock, so timing doesn't drift, even over a long session. Swipe the number to fine-tune the tempo, tap − / + to move one BPM, or tap the number to type it in. 20–300 BPM, with tap tempo.

LISTEN: FIND THE BEAT OF A SONG
Play some music and tap Listen. BeatLock listens through the microphone for a few seconds, estimates the tempo and where the beats fall, and takes over only when it's confident. If it isn't sure, it won't guess. Once it locks, nudge the beat anytime; the BPM never changes.

YOUR RHYTHM, YOUR WAY
Set the time signature, beat grouping and note value separately, so 7/8 can run as 2+2+3. Add subdivisions, rhythm patterns and swing. Tap any beat to switch it between accent, normal and mute.

LATENCY CALIBRATION
Every device and every output has its own delay, and Bluetooth headphones add the most. BeatLock keeps a separate latency offset for the speaker, wired headphones and each Bluetooth device. On the speaker, measure it automatically with a test tone; with headphones, fine-tune it by ear. Set it once per pair and it applies every time they connect.

TRAINING
Timer and count-in for every session. Training plans: a tempo ramp that builds speed step by step, silent bars that test your inner clock, and an offbeat click. A practice log keeps track of your sessions.

APPLE WATCH
Feel every beat on your wrist. Your iPhone sends the beat grid once and the watch keeps time on its own. Keep BeatLock open on your watch and it keeps tapping even after you lower your wrist. Adjust vibration strength and timing offset in Settings.

FREE
• 20–300 BPM and tap tempo
• Any time signature, common groupings and subdivisions
• Tap a beat to accent or mute it
• All 8 sounds
• Presets: save a setup and apply it in one tap (up to 3)
• Timer and count-in
• Screen flash and haptic feedback on controls
• Manual latency offset and beat nudge
• Background playback

MEMBERSHIP: GO AND PRO
Go unlocks the full metronome: custom beat grouping, rhythm patterns, swing, tempo ramp, big beat count view and unlimited presets.
Pro includes everything in Go, plus Listen, automatic latency calibration, silent-bar and offbeat training, and the practice log.
Subscribe monthly or yearly, or buy once for lifetime access. Try Listen free 10 times before you join.
Subscriptions renew automatically unless canceled at least 24 hours before the end of the current period. Manage or cancel anytime in Settings › Apple Account › Subscriptions.

PRIVACY
The microphone is on only during Listen and automatic calibration. Audio is processed entirely on your device: never recorded, never uploaded, never logged. No ads, no account. Anonymous usage statistics only, and you can turn them off in Settings.

Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/
Privacy Policy: https://peterchen1997.github.io/beatlock-site/privacy.html