In his youth Munro showed a high level of musical aptitude, mastering percussion, trumpet, and harmonica. He performed in a drum and bugle corps sponsored by the American Legion, the Sons of the American Legion Drum and Bugle Corps, eventually becoming the corps' drillmaster. Munro was also a member of Cle Elum's Boy Scout Troop 84. He attended Cle Elum High School, where he was a member of the school's wrestling team. Following his 1937 high school graduation, Munro enrolled in the Central Washington College of Education due to its proximity to Cle Elum, so that he could continue performing in the Sons of the American Legion. Munro was a yell king (a male cheerleader) at Central Washington.