Keep in mind that the same Psalm might well be sung in several different tones, depending on the tone of the Antiphon sung with it.
These tones are not fixed, even in the Extrordinary Form.
And the text of the Breviary Psalms have never been exactly that of the Vulgate, even before the Pius XII Psalter.
And this applies to differences in text between the Missale and the Graduale. Not uncommonly are these texts not the same.
