Псалтирь is an Android application that allows users to read the Psalms in Church Slavonic in both conventional and modern outlines. In addition, users can view the King James translation of the Psalms by clicking on the title of the psalm. The app also includes common prayers and prayers for the dead, such as "Six Psalms," "Chin read 12 psalms," "pomyannik," and "The Service at the end of the soul from the body." There is also a section "About psalmody" and a dictionary of obscure words to help users better understand the text.

The app has different reading modes, including single page (book), vertical, and night modes. Users can adjust font size, spacing, hyphenation, and typeface in the settings. They can also create bookmarks, view their reading history, and select their favorite psalms. Overall, Псалтирь is a useful app for those who want to read the Psalms in Church Slavonic and learn more about psalmody.