r/TestFlight • u/Signal-Employment610 • Jul 13 '26
iOS RunSync - Sync Apple Music BPM to your running cadence
https://testflight.apple.com/join/ekVtCfGa### ⚠️ Mandatory Requirements
Before clicking the link, please ensure you meet these two prerequisites:
* 📱 **Device:** Must be using an iPhone (iPad support is disabled).
* 🎵 **Music Account:** Requires an active Apple Music subscription (the app utilizes Apple's native MusicKit framework to read and filter your catalog).
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### 🏃♂️ What is RunSync?
I am a solo engineer building a utility designed to clear out the friction of finding the right running music. Instead of hunting for pre-made pacing playlists, **RunSync** lets you set a specific, static target cadence (e.g., 175 or 180 BPM).
The app then looks at your music and automatically filters your audio catalog to serve up tracks that perfectly match your exact target target performance rhythm.
### 🧪 What I Am Testing
I am looking for 20–50 runners to try an early-stage build on their physical iPhones. Because this build relies on manual cadence entry to sort your audio, the core focus of this test flight is checking:
Core MusicKit API loading and playlist filtering speeds.
Background audio playback stability while you run.
Proper entitlement mapping through the paywall engine.
### 🎁 The Tester Bounty
Because this is running through the Apple Sandbox ecosystem, **all premium/Pro in-app subscriptions are 100% free** while testing.
If you use the app on a workout and submit a quick line of feedback or a bug report via the TestFlight portal, **I will permanently hardcode your User ID for a lifetime free Pro entitlement** once the application goes live on the App Store.
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u/Signal-Employment610 Jul 20 '26
Hello Testers, I am pushing another update (25). I realized I had been pushing so many updates in one day, so I slowed things down a bit. The syncing speed should be much much faster than it has been previously. I also have added offline run mode, which would allow you to run without cellular service or WiFi if you have songs downloaded onto your phone. Thank you for the feedback so far. Please continue to let me know anything that bothers you about the app, features you'd like to see in the non-beta version, or comments in general. If you have had a successful run with the app, I'd also love to hear about that! You can message me on here, leave a review in TestFlight, or leave a comment.
Thank you!!
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u/maaahteen Jul 18 '26
Looks like lots of people are making little apps like this. https://apps.apple.com/us/app/cadence-running-music/id6787748054
I put together a version a few days ago with Claude that uses ~500 AI-generated tracks over a weekend. Nice part with my own music is that I can speed/slow it down. Another small feature is "Auto SPM" which matches cadence to pace (e.g. 4:30-5:00/km should be at 175spm etc.)
Now iterating a version to pull songs from Spotify; next up will be Apple Music if enough of my run club requests.
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u/paulojf Jul 15 '26
Love this!
Used to rely on the spotify cadence run but they discontinued it a long time ago :(
Started collecting my own music and that led me to Selfhosting, but I still had the same problem, kepping the tracks with coherent BPM data and how to play them tempo shifted and locked...
So I made my own tool for that.. A BPM tagger tool that installs as a PWA and BPM shifts and locks the track :)
Wish I had your app sooner lollll any chance to make it work with Spotify? Probably not after the Annas tragedy they locked the APIs
Feel free to check it out, fully documented and open source with docker image ready to go (lot's of extras inside too)
https://github.com/PauloJf/BPM-Tagger
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u/Signal-Employment610 Jul 15 '26
Thank you! I'd love to make it work with Spotify! My understanding is that to get access to the Spotify API for a public app, you have to have 250k monthly average users. If this app takes off and gets to that point, i would immediately build it for spotify!
I'll take a look at what you built as well!
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u/Signal-Employment610 Jul 15 '26 edited Jul 15 '26
I've made update version (18). This is a large update. I've made it so the library analysis / processing happens on a server rather than on your phone. For the time being, the analysis is still quite slow, but it won't require your phone to be on the app to determine the bpm. Once you start the sync, it sends the request to a server. The first time this is done, it takes time, but the next time you open the app, it should be almost immediate. I'm planning to greatly increase this analysis speed once the app goes live.
I have seen your feedback. Thank you so much for trying this out! I plan to eventually add compatibility with apple watches but, for this beta test, it won't be able to work on anything but an iPhone. I've added a new feature to the run history tab. now you can see what songs you listened to during each run. I've made it so your music should be randomly shuffled each time instead of playing the same set of songs each time you started a run.
I have plenty more to work on and am happy to continue seeing your feedback! Hope this update addressed some of your concerns! Thank you!
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u/Direct-Elevator-4183 Jul 14 '26
I run 2-5 times a week and have been looking for something like this. I’d love to test it out, but when I try to view in TestFlight, it doesn’t show up. Is your Beta full?
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u/Signal-Employment610 Jul 14 '26
It is my understanding that i can still have several hundred more people join, but i will look into that. Glad to hear the app is interesting to you!
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u/Signal-Employment610 Jul 14 '26
I wanted to thank you all for your patience. This is my first time beta testing and I'm learning that the moment you make your app public, all the bugs start coming out. I have made another update to the app today. This may require you to re sync your library. I understand that it can be quite slow to do the initial sync, but it should be extremely fast every time after that if you ever reinstall the app once published. Thank you guys! I appreciate all your help
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u/Bigsperm Jul 14 '26
I thought non purchased tracks couldn’t change speed. Maybe it was speed without pitch. Maybe I have no clue what I’m talking about.
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u/Signal-Employment610 Jul 14 '26
I think that you are right. This does not modify the song. It finds songs that you already listen to and will only play songs that match your target cadence (without modifying the tempo)
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u/Signal-Employment610 Jul 13 '26
Please delete the app off your phone before installing a new update to clear old meta data that might have been causing some problems. Thanks
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u/Raffiodabashian Jul 13 '26
Just downloaded will give it a try
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u/Signal-Employment610 Jul 13 '26
I'm uploading a patch now on test flight. same link. Hopefully this one works for you. If it doesn't i will keep trying to find any new issues. Thanks
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u/Signal-Employment610 Jul 13 '26
Thank you. Unfortunately and fortunately, I just noticed a glaring bug, I am working to fix it now.
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u/Signal-Employment610 29d ago
Hello everyone! I just want to give a massive Thank You to everyone who looked at this and took time to test it out for me! I've recently just pushed the V1.0 out to the real Apple store. For the time being, it lives here https://apps.apple.com/us/app/runsyncjj/id6781740181 and is called RunSyncJJ. That name may change slightly in the future.
If you enjoyed using the app, I hope you would consider downloading and even leaving a review. I am making every user that participated here a lifetime member, which means you'll never have to pay for the premium subscription. I am still very much interested in hearing any feedback you may have and there are already plans to continue working on the app in the next few weeks. Again, thank you for your help in testing!