By comparing primary sources for late renaissance and early baroque trumpet playing, such as Bendinelli’s Tutta l’arte della Trombetta, Fantini’s Modo per Imparare a sonare di Tromba and Praetorius’ Syntagma Musicum III, and examining original instruments and mouthpieces from the 16th and 17th centuries, we gain a deeper understanding of how the music from the Thomsen and Lübeck manuscripts was played at the court of Christian IV of Denmark, and how it can be made accessible to the trumpet players of today. By studying the manuscripts, we do not only learn how to play magnificent trumpet sonatas for ensembles of 5 or more trumpets as they were played at royal courts in the late renaissance, but we also start to understand the military nature of trumpet playing during the period and how it affected the music. Christian IV’s great wealth and thirst for projecting his power, through war and art, led him to employ a significant number of trumpeters throughout his reign, with two of the oldest manuscripts containing music written for trumpets being produced at his court. Thus, his courtly trumpet corps is an ideal subject for the study of royal trumpet playing in the late 16th and early 17th centuries. By comparing the capabilities of historical trumpets to our modern ones, and by considering the culture of military playing, we get a closer idea of the sound which the trumpeters of the time made. The trumpet was ever a loud instrument and Girolamo Fantini described its sound perfectly: “This [player], with the sound of [his] bellicose instrument, at his will made helmets vacillate, spears shatter, and chargers, fiercer than lightning or the wind, shiver” 1 , and even the great masters of the instrument were compelled by their duties in war, Magnus Thomsen himself having fallen in battle in the Kalmar war of 1611-1613. On a more personal level, the process of doing this research has affected my own practice, as a historically informed trumpeter, not only when playing sonatas and military signals, but also when playing much later music, because remnants of the military style persisted in trumpet music at least well into the 19th century. My experimentation with improvising additional voices to the sonatas, and memorizing military signals and toccatas, has also greatly increased my confidence in my skills as an improviser and familiarity with my own instrument, the natural trumpet. In conclusion, through deeper knowledge of the performance practice of 16th and 17th century trumpet players, we may begin to understand the music of the Thomsen and Bendinelli manuscripts, and even improvise our own variations of their five part music without needing to rely on editions and arrangements.