Nothing is certain about the career of John Dunstable. Some of his earliest works date from c.1410-1420, which would approximate his birth somewhere in the late 1300's. It is widely held as true that Dunstable spent the years from 1422 to 1435 in France as a musician to the Duke of Bedford (a brother of King Henry V and Regent to France during those years).
Musically, Dunstable's significant contribution to the theory and practice of composition in the early Fifteenth Century was the introduction of more melodic music and outlining chords as a part of the melody. This incorporated a more tonal center in the his works and in the music as a whole. This also introduced leaps of a third or even the sixth as consonant and pleasing sounds to the ear. One such piece by Dunstable is the secular song "O Rosa Bella" which as Grout says in A History of Western Music, it can "illustrate the expressive lyrical melodies and the clear harmonic profile of the English music of his time." (135)
The presence of chant in this time period is still rather common. Dunstable is well known for his combination of the sequence "Veni sancte spiritus" with the hymn "Veni creator." This four-part motet is one of his most famous pieces. However, the work "Quam pulchra es"- which consists of three free voices, demonstrates Dunstable's creativity and ability to compose free of a chant melody. The three voices of this piece move in the same basic rhythm and ususally enunciate the same syllable to help outline a general form, but still move individually and lyrically.
Dunstable has also received credit for writing a number of carols. Carols are uniquely English compositions, that although not folksongs, have the quality of simple two- or three-part harmonies and melodies that emphasize the text. They also contain a refrain between each stanza. The text is either English or Latin, or both.
As suggeted by Martin Le Franc, John Dunstable was a prominent composer who influnced both the composers of his time, like Leonel Power, and those to follow, like Dufay and Binchois.