This is an excellent question to review the scarce and often fragmentary sources that we have of people of African descent in England during the Tudor period (and beyond). The scarcity of sources should not be considered evidence that there were few or no individuals of African descent in England, Scotland, or even the rest of Europe at this time. Biographical details are hard to come by and we only know of the people of African descent because they are noted as being of that origin. There are likely many, many more who weren't described as such being buried, getting married, or giving testimony in court.
Therefore, this answer will look at the source material only. For an extensive look into the context of John Blanke's life as well as many of his contemporary musicians of African descent in English and Scottish courts as well as the rest of Europe, please refer to the first chapter of Dr. Miranda Kaufmann's Black Tudors: The Untold Story.
We first meet John Blanke when he is being paid for his services to Henry VII. Blanke was paid 20 shillings for the month of November 1507. The document reads in part:
Item to John blanke the blacke Trumpet for his moneth wages of [November] last passed at viij d the day – [8d or 4p per day] xx s. [20 shillings].
Notice that Blanke is explicitly pointed out as a blacke Trumpet. This is typical of the sources that we are dealing with at this time, yet we are lucky. The closer the individual is to the royal court, the more sources we can tie to the person in question. For John Blanke, we have no biography. We don't know when or where he was born, how he came to England, or even if 'John Blanke' was his original name (and not just a name given to him in jest). Each source puts him in a royal context or addressing royalty. We see John Blanke performing (and being paid for) his royal duties both at the funeral of Henry VII and the subsequent coronation of Henry VIII. An intriguing document reaches us from the early reign of Henry VIII in which John Blanke petitions the King for an increase in wages. It reads:
To the King, our sovereign Lord,
In most humble wise beseecheth your highness, your true and faithful servant John Bla[n]ke, one of your trumpets. That whereas his wage now and as yet is not sufficient to maintain and keep him to do your Grace like service as other your trumpets do. It may therefore please your highness in consideration of the true & faithful service which your servant daily doeth unto your Grace and so during his life intendeth to do, to give and grant unto him the same room [position] of Trumpet which Dominic deceased late had, to have and enjoy th esaid room to your said servant from the first day of December last passed during your most gracious pleasure, with the wage of 16d by the day. And that this bill signed with your most gracious hand may be sufficient warrant and discharge unto John Heron treasurer of your Chamber for the payment of the said wage accordingly. And he shall daily pray to God for the preservation of your most noble and royal estate long to endure. [Transcript by Dr. Kaufmann, Black Tudors]
His petition was successful. We next find John Blanke in his most famous appearance: The Westminster tournament roll of 1511. The Westminster tournament took place on February 12-13 1511 in honor of the birth of Prince Henry. Blanke, in his position as a trumpeter, had an obligatory presence during the festivities and can be seen depicted twice on the tournament roll. This is an extraordinary inclusion, seeing as we do not have any other named individual of African descent depicted during this time period. That Blanke was described as the "blacke Trumpet" in 1507 has made it possible for historians to put two and two together. Had Blanke not been described as such, the probability is that we would still be scratching our heads trying to figure out who this man depicted on the tournament roll actually was.
We last meet John Blanke in 1512. Luckily, it is not a notice of death, but rather something more joyful: Marriage. We don't know who John Blanke married, but we know that he did enter marriage because Henry VIII sent him a wedding gift:
Warrant to the Great Wardrobe to deliver John Blak 'our trompeter.' A gown of violet cloth, &c. including a bonnet and a hat, 'to be taken of our gift against his marriage.' Greenwich, 14 January 4 Henry VIII. [Transcript by Imtiaz H. Habib, Black Lives in the English Archives, 1500-1677 (2008)]
After that, Blanke disappears. He is not mentioned again in royal records or anywhere else.
Yet we are lucky to have this much information. A more common archival trace of a black life in Tudor England would be that found in the registers of St. Andrews in Plymouth from 1583 that in one sentence writes about the burial of "Bastien, a blackmoore" who was buried on December 10th. Yet what is extraordinarily important about John Blanke is that he reinforces something that not a lot of people might be aware of: For people of African descent in England, or Germany, or the Netherlands during this time, it is not a story that begins or ends with slavery. John Blanke was not enslaved during his time in the court of Henry VII and Henry VIII. Furthermore, it is important to understand that John Blanke was not an aberration, a 'token black guy' in 16th century Europe. He joined thousands of other men, women, and children who in Tudor England alone was scattered across the country, from port cities to small villages.