In this is hidden the life of an artist's greatness.

And here the little song, which gives joy to a child, and fits in with and enhances its joy, is greater in the eyes of the immortal judges than all the glory of the world which Sordello sought so long for himself alone.

It is a truth Browning never failed to record, the greatness and power of the things of love; for, indeed, love being infinite and omnipotent, gives to its smallest expression the glory of all its qualities.
The second of these analogies between Browning and Sordello relates to Browning's treatment of the English language in the poem of _Sordello_ and what he pictures Sordello as doing for the Italian language in the poem.

The passage to which I refer is about half-way in the second book.
As there is no real ground for representing Sordello as working any serious change in the Italian tongue of literature except a slight phrase in a treatise of Dante's, the representation is manifestly an invention of Browning's added to the character of Sordello as conceived by himself.

As such it probably comes out of, and belongs to, his own experience.