I will incline mine ear to a parable. The psalmist is "like a minstrel who has to play a piece of music put into his hands. The strain is none of his own devising; and as he proceeds, each note awakes in him a mysterious echo, which he would fain catch and retain in memory" (Kay).
A "parable" in the Old Testament means any enigmatical or dark saying, into which much metaphor or imagery is introduced, so that it is only φωνᾶν συνετοῖσι. I will open my dark saying upon the harp; i.
e. with a harp accompaniment. Music was a help to inspired persons in the delivery of messages which they were commissioned to deliver (see 1 Samuel 10:5; 2 Kings 3:15).