Complex sentence: Later he worked with multi-national jazz bands like Kurt Edelhagen's and in 1961 he founded The Kenny Clarke-Francy Boland Big Band with drummer Kenny Clarke, which rapidly became one of the most noted Big Bands to have been assembled outside the United States.
Split into simpler sentences: Later he worked with multi-national jazz bands like Kurt Edelhagen's and in 1961 he helped found a multi-national Big-Band with drummer Kenny Clarke. Their The Kenny Clarke-Francy Boland Big Band is among the most noted Big Bands to have been assembled outside the United States.