Liber Pro brings the 1961 Liber Usualis, a comprehensive collection of Gregorian Chants, to your iPhone, iPad, or iPod Touch. This app enhances the original tome with features like a linked table of contents, user-defined bookmarks, vertical and horizontal paging, zooming, browser-like navigation, and a dynamic liturgical calendar. It serves as more than just an eBook by integrating a complete 1961 Roman Calendar, automatically calculating moveable feasts throughout the year. With Liber Pro, users can easily navigate through the chants and liturgical calendar with efficiency and precision.

The app offers a user-friendly browsing experience with touch gestures for scrolling, zooming, and paging. Additionally, features like bookmarks, table of contents, search functionality, annotations, and a history section further enhance the usability and accessibility of this unique resource for Gregorian Chant enthusiasts.