Complex sentence: In a changing world of jazz, Panassié was a ardent exponent of traditional jazz--strictly Dixieland--in a style similar to that of Louis Armstrong from the 1930s.
Split into simpler sentences: In a changing world of jazz, Panassié was a ardent exponent of traditional jazz--strictly Dixieland. He harbored a particular love of style similar to that of Louis Armstrong from the 1930s.