He was a prolific and highly regarded composer at the time, but little of his work survives, almost all having been destroyed in the Lisbon earthquake and fire of 1755.
Ghersem was born in Tournai, and received his boyhood musical training there, possibly under the direction of composer George de La Hèle.
During this period, as during the previous two hundred years, the Low Countries provided a dependable source of talented young musicians for the choirs of kings and aristocrats in other parts of Europe.
During this time the court in Brussels was one of the leading artistic centers in Europe; this was the beginning of the "Golden Age" in the southern Netherlands.
Some of his distinguished musical colleagues in Brussels in the early 17th century included Peter Phillips and John Bull.