He collected more than 400 folk melodies, basing on them his best-known compositions, especially the Misa Criolla . Made entirely from traditional rhythms (the vidala-baguala, the carnavalito, the chacarera trunca, the carnaval cochabambino and the estilo pampeano), Misa Criolla was also one of the first masses to be celebrated in a modern language, since it is contemporaneous with the Second Vatican Council. Ramírez completed the Mass in 1964; it was recorded that year, but was not publicly performed until 1967.