What was a critical new technology that aided the study of folk music in the early 20th century?

A critical new technology that aided the study of Folk Music in the early 20th century was the phonograph. Invented in the late 19th century, this device allowed researchers and ethnomusicologists to record and preserve traditional music in its authentic form, capturing the nuances of performance and oral traditions. By enabling the documentation and dissemination of folk music, the phonograph played a pivotal role in the revival and appreciation of cultural heritage during that period.