The chants which are used during this ceremony are exceedingly fine. First of all, there are the Improperia, that is, the Reproaches made by our Saviour to the Jews. Each of the first three stanzas of this plaintive Hymn is followed by the Trisagion, or Prayer to the Thrice Holy God, who, as Man, suffers death for us. Oh ! let us fervently proclaim him to be The Holy, The Immortal ! This form of prayer was used at Constantinople, so far back as the fifth Century. The Roman Church adopted it, retaining even the original Greek words, to which, however, she adds a Latin translation. The rest of this beautiful chant contains the comparison made by our Lord, between the favours he has bestowed upon the Jewish people, and the injuries he has received from them in return.
(The Liturgical Year: Passiontide and Holy Week (Dom Prosper Gueranger; 1886)