[2] Greenberg, although self-taught, had been conducting amateur choruses such as that of the International Ladies' Garment Workers Union, and by 1950 was known as a choral conductor.
When Pro Musica was formed, it was a sextet and included the countertenor Russell Oberlin; labour activist and leftist Jesse Simons was one of the first members of the board of directors.
In 1953 William Kolodney booked the ensemble for a three-part performance series at the 92nd Street Y, contributing to the group's early momentum.
[2] Terry Teachout, writing in 2001, said "New Yorkers who attended his concerts in the 50’s and 60’s will need no reminder of the pivotal role he played in introducing early music to a generation of American listeners.
"[2] His "staging of The Play of Daniel, an 11th-century liturgical drama that had not been performed for 700 years before being presented by Greenberg in 1958 ... is still remembered as one of the key moments in the history of the early-music revival."