Campion made a nuncupative will on 1 March 1619/20 before 'divers credible witnesses': a memorandum was made that he did 'not longe before his death say that he did give all that he had unto Mr Phillip Rosseter, and wished that his estate had bin farre more', and Rosseter was sworn before Dr Edmund Pope to administer as principal legatee on 3 March 1619/20.
While Campion had attained a considerable reputation in his own day, in the years that followed his death his works sank into complete oblivion. No doubt this was due to the nature of the media in which he mainly worked, the masque and the song-book. The masque was an amusement at any time too costly to be popular, and during the commonwealth period it was practically extinguished. The vogue of the song-books was even more ephemeral, and, as in the case of the masque, the Puritan ascendancy, with its distaste for all secular music, effectively put an end to the madrigal. Its loss involved that of many hundreds of dainty lyrics, including those of Campion, and it was due to the work of A. H. Bullen (see bibliography), who first published a collection of the poet's works in 1889, that his genius was recognised and his place among the foremost rank of Elizabethan lyric poets restored.
Campion set little store by his English lyrics; they were to him "the superfluous blossoms of his deeper studies," but we may thank the fates that his ideas on rhymeless versification so little affected his work. His rhymeless experiments are certainly better conceived than many others, but they lack the spontaneous grace and freshness of his other poetry, while the whole scheme was, of course, unnatural. He must have possessed a very delicate musical ear, for not one of his songs is unmusical; moreover, his ability to compose both words and music gave rise to a metrical fluidity which is one of his most characteristic features.
Rarely are his rhythms uniform, while they frequently shift from line to line. His range was very great both in feeling and expression, and whether he attempts an elaborate epithalamium or a simple country ditty, the result is always full of unstudied freshness and tuneful charm. In some of his sacred pieces, he is particularly successful, combining real poetry with genuine religious fervour. Some of Campion's works could also be quite ribald – such as "Beauty, since you so much desire".
Early dictionary writers, such as Fétis, saw Campion as a theorist. It was much later on that people began to see him as a composer. He was the writer of a poem, Cherry Ripe, which is not the later famous poem of that title but has several similarities.
In popular culture
Repeated reference was made to Campion in an October 2010 episode of the BBC TV series, James May's Man Lab (BBC2), where his works are used as the inspiration for a young man trying to serenade a female colleague. This segment was referenced in the second and third series of the programme as well.
Occasional mention is made of Campion ("Campian") in the comic strip 9 Chickweed Lane (i.e., 5 April 2004), referencing historical context for playing the lute.