It was only in April 1943 that Hindemith was able to realise his plans to rehearse and perform works of Early Music with a "Concert of 17th-Century-Music" given by the Collegium Musicum. The ensemble was made up of his own pupils as well as external members (Gertrud Hindemith also sang in the choir). By 1953 the Collegium Musicum had presented a total of twelve concerts of Early Music at which the works they performed included songs of Oswald Wolkenstein, masses and motets of Dunstable and Dufay, French chansons, madrigals and masses of Italian composers, but also instrumental works of different centuries.
Hindemith made efforts to perform the works with the greatest possible historical authenticity and thus became a pioneer of historical performance practice in the United States. He himself took on the often tedious task of preparing the old manuscripts for performance. He appeared as conductor at the concerts, and as instrumentalist during the initial years as well. As required, he played the vielle, viola da gamba, viola d'amore or bassoon.
The concerts of the Yale Collegium Musicum was one of the special attractions of each academic year, as stated in a student survey: «The Collegium Musicum is apparently regarded as the most outstanding musical experience that one can experience at the University.»