1)Why were there THREE themes to the series?(Two instrumental,and one vocal(the 1966-1967 instrumental theme was the best,the instrumental theme used in the 1967-1968,1968-1969,and 1969-1970 was also good,but I did NOT care for the 1970-1971 vocal version.Why was the last season vocal?and THREE producers-Jerry Davis(first),Danny Arnold(season 2)and Saul Turteltaub and Bernie Orenstein (seasons 3,4,and 5)?