What Sheet Music Library does The Sheet Music Library app will open and read PDF files that you specify for the purpose of displaying the pages on the screen. The app will copy the PDF files to the folder you specify for the book you choose to store the PDF files in. The app will also collect metadata about the PDF files (number of pages and page dimensions) and store that data in the book folder as well.
What Sheet Music Library does not do The Sheet Music Library app will not collect any information about you or the contents of any of the PDF files you open with the app. It will also not transmit any information (including book data) over the internet or any other network.
Use of the app with cloud-based storage If you choose a folder for a book that is part of cloud-based storage (like OneDrive, Drop Box, Google Drive, etc.), then the cloud provider will collect and transmit the book data and the PDF files for the book to its cloud storage (as outlined by the provider). But the Sheet Music Library app is not involved in the transmission in any way.