Complex sentence: Her record producer during 1963 to 1965 was Quincy Jones, whose dentist was Marvin Hamlisch's uncle, and Hamlisch asked his uncle to convey several songs to Jones.
Split into simpler sentences: Her record producer during 1963 to 1965 was Quincy Jones. Jones'dentist was Marvin Hamlisch's uncle, and Hamlisch asked his uncle to convey several songs to Jones.