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Why Your Metronome Stops When Your Phone Locks (and the App That Keeps Playing)
It always happens at the worst moment. You are eight bars into the take, the singer says lock it in, the phone screen goes dark so you can put it in your pocket, and the click dies about ten seconds later. Or worse: it survives the lock, then someone calls you, the ringtone murders your tempo track, and when you hang up the metronome never comes back. You are left tapping your foot against silence, wondering what 127 BPM felt like.
If you have searched for a fix, you have probably landed on a thread about battery optimization. Those threads are mostly about Android. On an iPhone the reasons are different, and knowing them helps you pick an app that does not betray you halfway through a rehearsal.
Why the click dies when the screen goes dark
iOS allows audio apps to keep playing in the background, but the app has to declare it and behave correctly. A metronome that only plays sounds while it is the front app will get suspended the moment the system needs memory for something else. What the app does in those seconds decides everything.
The failure modes are predictable:
- The app stops its audio engine when it loses focus, and restarts it on resume. Fine for a music player. Useless for a click, because the resume only happens if you reopen the app.
- The app keeps a timer instead of an audio clock. Timers drift and get throttled once the screen locks, so the click that comes back is late, and a late click is worse than no click.
- The app never planned for interruptions at all. A phone call arrives, iOS pauses every audio session, and the app has no listener waiting to press play again when the call ends.
The third one is the killer. Your phone does not ask before interrupting. A call, a Siri trigger, a pulled headphone cable, a CarPlay connection, each of them pauses your audio session. What the app does after the interruption is the entire story.
What to check in your current app
Before you switch anything, run three tests tonight. They take five minutes and they tell you exactly where you stand.
Test one: start the click, lock the screen, and wait a full minute. If the sound stops, or if it stutters when you unlock, the app is not handling background audio properly.
Test two: start the click, then phone yourself from another device. Decline the call. Does the click come back by itself, at the right tempo, without you touching anything? Most apps fail here, and this is the exact scenario that ruins a session when your drummer's girlfriend calls mid-take.
Test three: start the click, then unplug your headphones while it plays. iOS pauses everything on a headphone pull. An app that respects its musicians brings the click back through the speaker, at the right tempo, on its own.
If your app passes all three, keep it. Seriously. A click you can trust is worth more than any feature list.
A metronome built to survive calls
I work on GroovePilot, and this failure mode is the reason the app exists. The click keeps playing with the screen locked, and when a phone call or a Siri interruption or a headphone pull stops the audio, the click comes straight back on its own. No tapping the screen, no navigating back to the app, no counting the band back in.
The details are on the boring side but they matter. The timing runs off the audio clock rather than a timer, so a locked phone does not drag the beat. The click plays in the same audio session as your other apps, which means you can run a backing track in one app and the click keeps running alongside it, mixed rather than fighting. And the tempo you set on the phone follows to the Watch if you wear one.
There is a mute-across-calls detail I like too: the app is fully offline and collects no data, and the microphone is only ever listening while you are using the BPM counter or the tuner. If you are privacy-minded, that is the whole sentence you need.
The habit worth keeping
Whatever app you land on, build the three tests into your routine. Run them after every iOS update, because a new OS version is exactly when background audio behavior changes and apps that used to pass start failing silently. Run them before every gig. The lock-screen test costs you sixty seconds and it is the difference between a click you trust and a click you babysit.
A metronome is the one piece of gear where reliability is the entire feature. Tempo range, subdivisions, polyrhythms, all of that is decoration if the thing stops when a phone call comes in. Get the behavior right first, then go shopping for extras.
GroovePilot is free on the App Store if you want to run those three tests against it: https://apps.apple.com/app/id6823979251
Questions we get
Will my metronome keep playing while I am on a phone call?
Ordinary apps stop, because iOS pauses their audio when a call starts. GroovePilot auto-resumes the click the moment the call ends, so you are back on tempo without touching anything.
Why does the click stop when my iPhone locks?
Most metronome apps run their timing off a plain timer, and iOS throttles timers in the background. The click has to be built on a proper audio clock to survive the lock screen.
Does GroovePilot work offline?
Yes. No account, no network needed, and the click keeps going in airplane mode.
Is the phone metronome free?
Yes. The metronome, tuner and BPM counter are free with no ads. Pro extras like the Apple Watch app and MIDI sync are a one-time purchase, not a subscription.
This blog is written by the team that builds GroovePilot. We are working musicians who got tired of metronome apps dying at the lock screen, so we built one that does not. Every claim in these posts was tested on a bandstand first, not in a demo video.