Hofmann was born in Kyle, Texas on a cotton farm. He was the youngest of 10 children of German immigrants, Wilhelm and Friede Hofmann. Otto attended Kyle High School and was valedictorian for his 1936 class. He received a bachelor's degree in and a master's degree in Choral Direction at the University of Texas. He was working on his doctorate when he was drafted. Being a conscientious objector, he was sent to Civilian Public Service Camp. After a brief marriage in the mid-1940s that resulted in two daughters, Helene and Pam, he returned to the family farm in Texas to resume his organ building career. In 1949, he traveled to Aspen, Colorado to hear Albert Schweitzer speak. There he met a young German woman, Margarete Schultze, who was helping Schweitzer with translation. She was a war refugee who had also traveled to hear Schweitzer speak. A year later, Otto invited her to Texas. He wanted to go to Germany to look up long lost relatives and she was homesick and wanted to return to Germany for a visit. In 1950, they were married in Berlin, Germany and Margarete Schultze became Margret Hofmann. They returned to Texas and had five children: Franz, Barbara, Anna, Heidi and Stephen. Over the years they accumulated many grandchildren and great grandchildren. In 1977, Otto and Margret divorced, but remained close friends until his death. Otto joined the AustinFriends Meeting in 1954 and was a central figure in the meeting until his death.
Otto's organ building career began officially in 1947 but he built his first organ in 1937 when he was just 18 years old for his home church of Immanual Baptist Church in Kyle, Texas. In 1954 he moved to Austin from Kyle to expand his company. His largest organ was built for Margarete B. Parker Chapel at Trinity University in San Antonio, Texas. In 1980, he was elected as the first American president of the International Society of Organbuilders. After a heart attack in 1988, Otto retired from organ building decided to do a little acting. He died at the age of 82. David J. Polley of the University of Nebraska wrote his 1993 doctoral dissertation on Hofmann's organ-building career, the abstract of which is quoted here in full:
