Why is the song incomprehensible to poet in The Solitary Reaper?

In the poem "The Solitary Reaper" by William Wordsworth, the poet does not find the song of the Highland girl incomprehensible. Instead, he is captivated by the beauty of her Gaelic song, even though he does not understand its specific words. In the poem, the poet describes the "language of sorrow" expressed in her song, using phrases like "wild and passionate", "mournful cadence", and "plaintive numbers". His focus is on the emotional impact and the "unremembered pleasure" evoked by the melody, rather than any literal comprehension of the lyrics.