Jean-Adam Guilain (real name Johann Adam Wilhelm Freinsberg) (c. 1680 – after 1739) was a German organist and harpsichordist who was mostly active in Paris during the first half of the eighteenth century.
Little is known about his life. He was born in Germany, possibly around 1680 (the exact dates of birth and death are unknown). For an unknown reason he moved to France some time before 1702, and almost certainly became one of Louis Marchand's pupils - Guilain's organ collection is dedicated to Marchand, by then a prominent organ teacher. Guilain died some time after 1739, the year when he published a collection of harpsichord pieces.
A single collection of organ pieces (Pièces d'orgue pour le Magnificat sur les huit tons différents de l'église) was published in 1706 in two volumes, of which only one is now extant. The full collection included eight suites of pieces for use with the Magnificat, one suite for each church mode.
- from Wikipedia