Complex sentence: The Ian Campbell Folk Group were one of the most well known and influential folk groups of the British Folk Music Boom of the 1960's with many appearances, on radio and TV, and at national and international venues and festivals.
Split into simpler sentences: The Ian Campbell Folk Group were one of the most well known and influential folk groups of the British folk music boom of the 1960s. The group made many appearances on radio, television, and at national and international venues and festivals.