It is possible that Mercker was trained by Conradus who had been a student of Sweelinck. Mercker became an instrumentalist and composer with his first reported performances and interests focusing on the cornett. At this time he was in service to King Christian IV of Denmark and in 1602 he travelled to Russia in service to Christian's brother. Upon his return to Denmark, his post with the king had been assumed by another musician so Mercker became an organist in Franeker. By 1608 he he had moved on and had become the cornet player for the Duke of Holstein. In his dedication to "Musica instrumentalis" Mercker mentioned Munchhausen who it seems he served for three years. The last reports in reference to his musical service indicated that he was the organist of St Nicolaus Church in Strasbourg. It is clear that he was a skilled and artistic instrumentalist playing the organ, trombone, cornett, flute and viol. Compositions by Mercker also demonstrate a keen awareness of musical theory and artisanship with an emphasis on instrumental dances.
Keith Johnson, All Music Guide