Isaac was born in
Pioneer, Iowa on October 12, 1898 to William P. and Elizabeth J. Isaac. Merle was of
Welsh and
Scottish descent; his mother emigrated from Scotland as a child his paternal grandparents were Welsh. Shortly before 1900, the Isaac family moved from
Iowa to
Illinois. Isaac's parents later bought a piano and he continued studying piano and organ with Carnduff until he finished eighth grade. Isaac enrolled at Crane Junior College, now known as
Malcolm X College. After attending classes there in the morning, he dedicated his afternoons to practicing the church organ. This led him to a weekend job accompanying
silent films on organ at movie theaters in the area. Isaac was hired at one theater on December 26 after the previous organist missed Christmas day. After a few months working there, he switched to a theater closer to home which showed daily matinees. To keep up with the quickly changing mood of the film, he often memorized or improvised the soundtrack. He began writing down his improvised melodies and the different registrations he used. During this time, Isaac also began studying organ,
harmony, and
counterpoint with J. Lewis Browne. Isaac's theater organ experience enhanced his understanding of harmony, facilitating his later career as an orchestral arranger. ==Music and recognition==