We know very little about the English composer and astronomer John Dunstaple (also spelled Dunstable). He worked at the court of the Duke of Bedford, with whom he travelled through France in the early 15th century, and at the court of the Duke's brother, the Duke of Gloucester. What has been preserved, however, is his tomb slab with the original Latin inscription:

"Here he lies, enclosed in this tomb; he who enclosed the heavens in his breast, John Dunstable, ally of the stars. Through his counsel, Urania knew how to elicit secrets from the heavens. This man was your glory, your light, your leader, your music. In the year 1453, on the day before Christ's birth, he passed away to the stars. May the citizens of heaven receive him as their equal."*

The masses and motets by John Dunstaple, which were widespread in Europe at the time (manuscripts of Veni sancte spiritus / veni creator spiritus can be found in Modena, Trento, Aosta and Munich, for example), are the first evidence of the transition from medieval music to the Renaissance. Influenced by English folk music, jarring dissonances in liturgical music are increasingly resolved harmoniously into thirds and sixths, establishing a consonant harmony that continues to dominate popular music today.
In the isorhythmic motet ‘Veni Sancte Spiritus / Veni Creator Spiritus’ for four voices, rhythmic, melodic and textual structures overlap and are combined with one another. This results in a melodious euphony that unifies details such as texts, imitations or rhythmic figures on a higher level and creates a feeling of new expansiveness. Words and texts become meaningless in the face of something higher, and the musical sound itself can serve the conscious listener to open themselves freely to the reality that tradition invokes with the terms ‘Sancte Spiritus’ and ‘Creator Spiritus’: Holy Spirit and Creative Spirit.

* Clauditur hoc tumulo, qui caelum pecore clausit, / Dunstable Joannes, astrorum conscius. Illo / Iudice novit Urania abscondita pandere caeli.
Hic vir erat tua laus, tua lux, tibi, musica, princeps, / Quique tuas dulces per mundum sparserat artes. / Anno Mi. C. quater semel L tria iungito, Christi
Pridie natalem, sidus transmigrat ad astra. / Suscipant proprium civem caeli sibi cives.

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Because there were no partitures at that time, the singers had to orient themselves to the common rhythm in order to sing in coordination with each other.
The motet begins in two parts (with the superius and motettus voices) and then combines three different hymns. First, the two hymns with the same beginning, ‘Veni Sancte Spiritus,’ are sung. Shortly afterwards, the contratenor sings the third hymn, ‘Veni Creator Spiritus’, and the listeners' ears can usually only orient themselves to the upper voice or the common harmonic changes in sound. It makes perfect sense to concentrate on the sound and block out the lyrics, as these sounds open up large spaces and thus lead us from the details to the big picture.
For repeated listening, a word grid of this motet (see below) is helpful, as the words can be followed voice by voice. Translations of these beautiful old texts can be found on Wikipedia.
The three sections of this motet follow each other in a ratio of 3:2:1, meaning that they focus on the third, the final part and the end of the three hymns.