Complex sentence: Much of what is known about folk music, prior to the development of audio recording technology in the 19nth century, comes to us from fieldwork and writings of scholars, collectors and proponents.
Split into simpler sentences: Much of what is known about pre-recording-era folk music comes to us from scholarly fieldwork and writings. Most documented activity regarding folk music from the era prior to electronic recording, distribution and broadcast of folk music consists of the work of scholars, collectors and proponents.