Last updated: 1 October 2026. This policy explains what personal data the Music Theory Book app for iOS and iPadOS, and these pages on chordsandscales.app, collect about you, why, and what your rights are.
Music Theory Book is published by Sincere Apps SIA, a company registered in Latvia. For the purposes of the EU General Data Protection Regulation (GDPR), Sincere Apps SIA is the controller of the data described here. You can reach us about anything in this policy, including any request about your data, at sincere.apps@gmail.com.
The app has no account, no advertising, no analytics and no tracking. Everything you do in it, the pages you read, your scores, your mastery, the loops you compose, stays on your device. Only two things ever leave it: feedback you choose to send, and an anonymous crash report if the app crashes, which you can switch off in Settings.
If you use the feedback buttons in the app, you can send us a message by Mail or, when the device has no Mail, through a short form. In both cases we receive your message, together with the app version, your device model and operating system version, and the chapter you were on, so we can reproduce a problem. If you give your name or email address, we receive those too; both are optional in the form, and we use the address only to reply. Submissions made through the form are sent to our web server, archived there, and forwarded to our support inbox.
If the app crashes, it sends a crash report to Firebase Crashlytics, a service run by Google, so we can find and fix the fault. A report contains the device model, operating system version, app version, the point in the code where the crash happened, the last few pages you had open, and a random installation identifier that Crashlytics generates and that is not tied to your name, Apple ID or any advertising identifier. It never contains your progress, your sketches or anything you typed. You can switch crash reports off at any time in the app under Settings, About. We use no other Firebase service: no analytics, no advertising.
These pages use no cookies, no analytics and no tracking, and load no third-party resources. Our web host records standard server logs, including IP addresses, for security and troubleshooting.
If the app offers a purchase, it is processed by Apple. We never see your payment details, and Apple does not give us your name or billing address. Apple is an independent controller for the payment itself; see the Apple Privacy Policy.
We do not collect your name or address unless you tell us, your contacts, your photos, your location, or any audio. The app plays sound but does not record; it does not use the microphone. We do not use any third-party analytics service, and apart from the Crashlytics installation identifier described above, the app does not identify you with any identifier, random or otherwise.
We do not sell personal data and we do not share it for anyone else's marketing. Feedback is handled by our web host and by the email provider of our support inbox, who act on our behalf. Crash reports are processed by Google (Firebase Crashlytics) on our behalf. Apple handles payments. We may also disclose data if we are legally required to, or to establish or defend legal claims.
Our support inbox and Firebase Crashlytics are run by Google, with servers in the United States. That transfer is covered by the European Commission's Standard Contractual Clauses and the EU–US Data Privacy Framework, where applicable.
If you are in the EEA or the UK, you have the right to access your data, to have it corrected or erased, to restrict or object to how we use it, and to receive it in a portable form. Because we hold nothing about you unless you have written to us, the simplest request is to ask us to delete your messages. Email sincere.apps@gmail.com. If you think we have handled your data wrongly, you can complain to your local data protection authority; ours is the Latvian Data State Inspectorate (Datu valsts inspekcija), dvi.gov.lv.
The app is suitable for all ages and collects nothing from anyone, child or adult, beyond the feedback described above. If you believe a child has sent us personal data, contact us and we will delete it.
Feedback sent through the form travels over HTTPS. Archived submissions are stored outside the public web root. No method of transmission or storage is perfectly secure, and we cannot guarantee absolute security.
If we change what the app collects, this page and the app will say so before the change takes effect. The date at the top shows when it was last revised.
Questions, requests, or complaints: sincere.apps@gmail.com.