It has been suggested that because of the capitals and the book’s size, the Utrecht Psalter was intended as a choir book for several monks to read at the same time while singing; alternatively that it was intended for young monks learning the Psalms by heart in groups, a suggestion that perhaps better explains the amount of illustration.
Source: Utrecht Psalter – Wikipedia
See also: Method of Loci / Journey Method
Tim B.
“The style of the outline drawings is dramatic, marked by activity, leaping creatures and fluttering folds of drapery set in faintly sketched landscape backgrounds stretching the full span of a page. Unlike traditional medieval Psalter decoration, which focused on general narrative or symbolic aspects of the texts, the Utrecht Psalter provides a very literal, concrete depiction of every line of the text for each Psalm, all combined into one elaborate scene which directly precedes the psalm it illustrates. The purpose of this unusual mode of illustration is unclear. Some have argued it was designed to enable easier memorization of the psalm texts by associating every line with a striking image, in accordance with classical and medieval mnemonic arts (Gibson-Wood, 12-15).”