If someone who does not even know the meaning of the words recites Psalms, he is engaged in Written Torah.
He is dealing only with the letters of the text (even though he may not even be able to read), just as the sofer or scribe, who copies the Torah letter by letter is involved with Written Torah.
But as soon as someone begins to think about what the words mean, he becomes engaged in something else, in Oral Torah.
The problem seems to lie in the difference between contacting and connecting.
In order for us to understand, we have to establish intellectual connection with Written Torah, and that is Oral Torah.
The contact with the letters is not enough. The connection, which is Oral Torah, enables us to carry the Torah into our experiences of life.
–Rabbi Adin Steinsaltz