Sudip Bose at The American Scholar:
Few composers—in his time and in the centuries since—have been as deft as Purcell at marrying text and sound. His opera Dido and Aeneas is a seminal work, the most important of his compositions for the stage, and his songs, of which he wrote more than 100, are exemplary (such 20th-century English composers as Benjamin Britten and Michael Tippett would pay brilliant homage to them in their own ways). Between 1692 and 1695, Purcell composed three settings of Colonel Heveningham’s poem, all of them beautiful. The first two are more or less similar, but the third is a different work altogether, more florid, more darkly evocative.
It opens with a brief, enigmatic figure in the bass line, after which the soloist sings in the style of a recitative. As if to highlight the departure from Shakespeare (the exhortation in the text here is to Sing on, not play on), Purcell repeats that particular phrase, Sing on, each repetition becoming more and more embellished. The entire song is characterized by its melismatic style—that is, its use of melisma: the assigning of many notes, often in the form of an ornate run, to the singing of a single syllable.