Complex sentence: From 1948 to 1951, he regularly played Oscar Brand's Folksong Festival on WNYC, accompanying singers of many styles and ethnicities, which contributed to his eclectic style of guitar playing.
Split into simpler sentences: From 1948 to 1951, he played Oscar Brand's Folksong Festival on WNYC regularly, accompanying singers on his guitar. He played with singers of many styles and ethnicities, which contributed to his eclectic style of guitar playing.