When I cover the Cavalier Poets in my English literature class, I work from a textbook which uses the following as the third verse:

When, like committed linnets, I/ With shriller throat shall sing/ The sweetness, mercy, majesty/ And glories of my king;/ When I shall voice aloud how good/ He is, how great should be,/ Enlarged winds, that curl the flood/ Know no such liberty."

This, I think, is the verse to which Alan is referring.