Liber Pro

Liber Pro is a digital app that brings the rare and valuable Liber Usualis, the official chant book of the Church, to Apple devices. It offers a digital alternative to the physical book, with a calendar feature directing users to the correct page for each Liturgical Hour and the Holy Mass for the current Feast Day. The app also includes an annotation feature for marking the Liber, which can be hidden or displayed at will, reducing the risk of damaging historical books. Users can set bookmarks and return to marked locations, with a dark mode available for when a bright screen is undesirable. Liber Pro, initially developed by Michael Drake and now maintained by LiveMass and the FSSP, is offered free of charge. It features a browser with over 2,300 pages from the 1961 Liber Usualis, a calendar, user-defined bookmarks, a table of contents, a history of recently visited pages, and a text-based search feature. The annotation feature is available for both iPhone/iPod and iPad, with additional tools on the iPad.