Complex sentence: Sunset Sessions was founded by Michele Clark, who owned a radio promotion firm for over 20 years and has contributed to building the careers of artists by getting them radio airplay primarily in the Triple A radio format.
Split into simpler sentences: Sunset Sessions was founded by Michele Clark, who owned a radio promotion firm for over 20 years. Clark has assisted in building the careers of artists by getting them radio airplay primarily in the Triple A radio format.