«So oft have I invoked thee for my Muse
And found such fair assistance in my verse».
The poet’s success in gaining entry into the youth’s good graces inspires imitators: “As every alien pen hath got my use, / And under thee their poesy disperse.”
So oft have I invoked thee for my Muse
Acknowledging that he is being challenged by other poets for the young man’s affections, the poet asks the youth to compare these imitators’ verses against his own. Only then can the young man fully appreciate how wholly inspiring he is to the poet: “Yet be most proud of that which I compile, / Whose influence is thine, and born of thee.” For others, the youth merely improves their style — “In others’ works thou dost but mend the style”; for the poet, his young friend is “all my art” — subject, style, the reason for his writing the sonnets.
English audio from YouTube Channel Socratica
Summary from Cliffsnotes.com