Privacy Policy — Music Time Machine
Last updated: 19 September 2026
This policy explains what information the Android app Music Time Machine ("the app") handles, why, and what choices you have.
The app is published by ERISTO MARKETING BOUTIQUE SRL, Spl. Independenței nr. 313b, Corp C3, Parter, Ap. 6, Sector 6, 060042 București, Romania ("we", "us"). For questions about this policy or your data, contact us at eristoapp@gmail.com.
Short version
The app has no accounts, no login, and no server of our own. What you do in the app — which stops you have heard, which narrator voice you picked — is stored only on your device.
Three Google services inside the app do process data: AdMob to show ads, Google Analytics for Firebase to tell us how the app is used, and Firebase Crashlytics to report crashes. In the European Economic Area, the United Kingdom and Switzerland, all three stay switched off until you agree — one consent choice governs all of them, and you can change it at any time in Settings.
The music itself is never played by the app: you listen on YouTube or Spotify, in their own apps. The stories are read aloud by your phone's own text-to-speech voice.
We never see who you are. We see counts and averages.
1. What the app stores on your device
The following is saved on your phone or tablet only. It never leaves your device, we never receive it, and it is not backed up to any server we control:
- whether you have seen the three introduction screens;
- which stops you have heard to the end (the small blue tick in the app);
- which narrator voice you chose in *Settings → Story voice*, if you chose one.
Technically this lives in the app's local storage under a single key, mtm.state.v1. It is deleted when you uninstall the app or clear the app's data from Android Settings, and *Settings → Reset explored stops* clears the ticks on their own.
The app has no user accounts. We never ask for and never receive your name, e-mail address, phone number, contacts, photos or files. The app does not use your location, camera or microphone.
The narrator voice
The stories are read aloud by the text-to-speech engine already on your device (on most phones, Google's *Speech Services*). The app hands the story's text to that engine; it does not record or upload anything. By default the app chooses a voice that lives on the phone, so the text stays there. If you pick a voice that the app marks "Needs internet", the text of the story is sent to that voice's provider (Google) to be synthesised, under Google's own privacy policy.
1b. Usage statistics and crash reports
To understand how the app is used and to find bugs, the app uses Google Analytics for Firebase and Firebase Crashlytics (Google Ireland Limited for users in the EEA, UK and Switzerland).
In the EEA, the UK and Switzerland these are switched off by default and only start after you agree — the same consent choice that governs ads. If you decline, nothing below is collected.
What Analytics receives:
| Data | Why |
|---|---|
| An app instance ID — a random identifier for this installation, not for you | to count sessions and returning users rather than raw events |
| Device and app information — model, operating system version, language, approximate country (from IP) | to know which devices and regions to support |
| Which screen of the app is open | to see where people spend their time |
stop_opened — which stop, in which era | to see which parts of the journey people actually open |
song_link_opened — which stop, and whether YouTube or Spotify was chosen | to see whether people go and listen, and where |
intro_played — which stop | to know whether the "Hear this first" set-up is used at all |
story_started and story_finished — which stop | to measure how many stories are heard to the end, the one number that says the app works |
voice_chosen — only whether the narrator was left on automatic | to know whether the voice picker matters; never which voice |
interstitial_shown — how many stops since the previous ad, and which moment showed it (a story ending, the "Next stop" button, or the first minute of use) | to check the ad frequency is what we intended |
What Crashlytics receives, and only when the app crashes: the error and its stack trace, the app version, and the device model and OS version.
We do not send the text of anything, and there is nothing you can type into the app. No event carries a name, an e-mail address or a location. We cannot identify you from any of it, and we never try to.
The app instance ID is reset if you uninstall the app or clear its data. Google retains analytics data for 14 months; crash reports are kept for up to 90 days.
2. Advertising — Google AdMob
The app displays ads delivered by Google AdMob (Google Ireland Limited, Gordon House, Barrow Street, Dublin 4, Ireland, for users in the EEA, UK and Switzerland). The only format is an occasional full-screen ad between stops: when moving between screens after the first minute of use, and when a story ends. There are no banners, and an ad never interrupts a story.
To select, deliver and measure those ads, the Google Mobile Ads SDK inside the app collects and processes:
| Data | Why |
|---|---|
| Advertising ID (a resettable identifier unique to your device) | ad selection, frequency capping, measurement, fraud prevention |
| Device and app information — model, operating system version, language, screen characteristics, app version | ad formatting and compatibility |
| IP address, from which an approximate (city-level) location is derived | serving locally relevant ads and meeting legal requirements per country |
| Ad interaction events — that an ad was shown, viewed, closed or tapped | measurement and billing |
We do not receive this data ourselves in an identifiable form; we only see aggregate reports. Google processes it under its own policies:
- Google Privacy Policy — https://policies.google.com/privacy
- How Google uses information from sites or apps that use our services — https://policies.google.com/technologies/partner-sites
We do not sell your personal data, and we do not share it with anyone other than the advertising provider described above.
Your consent, and how to change it
If you are in the European Economic Area, the United Kingdom or Switzerland, the app asks for your consent the first time it runs, using Google's consent form. That single choice governs all three services — advertising, usage statistics and crash reporting. Decline, and none of them collect anything.
You can change that choice at any time: open Settings inside the app and select Privacy options.
Independently of the app, Android lets you limit ad tracking system-wide: Android Settings → Privacy → Ads, where you can reset or delete your advertising ID.
Note that ads are shown either way — declining means the ads you see are non-personalised, not that they disappear.
2b. Listening on YouTube and Spotify
The app does not host or play any music. Each stop offers a link that opens the song in the YouTube or Spotify app (or their websites) — the app hands over to them and plays no part in what happens there. Once you are in YouTube or Spotify, their privacy policies apply, not this one:
- YouTube (Google) — https://policies.google.com/privacy
- Spotify — https://www.spotify.com/legal/privacy-policy/
The app does not learn what you played there or for how long.
3. App updates
The app uses Expo Updates to deliver bug fixes without a full store update. When the app starts, it asks Expo's servers (Expo, 650 California St, San Francisco, CA 94108, USA) whether an update is available. This request contains technical information only — app version, runtime version, platform — and does not include your advertising ID or any information about how you use the app. Expo's privacy policy: https://expo.dev/privacy
4. Children
The app is intended for a general audience aged 13 and over. It is written to be enjoyable for families listening together, but it is not directed at children under 13, and we do not knowingly collect personal data from them. If you believe a child has provided personal data through the app, contact us at eristoapp@gmail.com and we will act on it.
5. Legal bases (GDPR)
Where the GDPR applies, we rely on:
- your consent (Art. 6(1)(a) GDPR, together with the ePrivacy Directive) for storing and reading the advertising identifier, for personalised ads, and for the usage statistics and crash reporting described in section 1b;
- our legitimate interest (Art. 6(1)(f) GDPR) in delivering a functioning, secure app and in preventing advertising fraud — limited to what is strictly necessary for that purpose.
You may withdraw consent at any time, as described in section 2. Withdrawal does not affect the lawfulness of processing carried out before withdrawal.
6. How long data is kept
Data on your device is kept until you delete the app or clear its data. We keep no personal data on any server of ours, because we operate none for this app. Advertising data is retained by Google under its own retention rules; analytics data for 14 months; crash reports for up to 90 days.
7. Your rights
Under the GDPR you have the right to access, rectify, erase, restrict and object to the processing of your personal data, and the right to data portability.
In practice, because we hold no personal data about you:
- to erase everything the app knows about you, uninstall it or clear its data in Android Settings — this also resets the analytics app instance ID, so no future data can be linked to the old one;
- to stop all collection going forward, open Settings → Privacy options in the app and withdraw your consent;
- for requests concerning advertising or analytics data already collected, contact Google using the links in section 2, since Google is the party processing it;
- for anything else, or if you are unsure, write to us at eristoapp@gmail.com.
You also have the right to lodge a complaint with a supervisory authority. In Romania this is the National Supervisory Authority for Personal Data Processing (ANSPDCP), https://www.dataprotection.ro.
8. Changes to this policy
If we change what the app collects, we will update this page and change the date at the top. Significant changes affecting advertising consent will be reflected in the in-app consent form.
9. Contact
ERISTO MARKETING BOUTIQUE SRL Spl. Independenței nr. 313b, Corp C3, Parter, Ap. 6, Sector 6, 060042 București, Romania eristoapp@gmail.com