Question: Who wrote the happy birthday to you tune?
Disambiguated questions and answers: question: Who is believed to have written the happy birthday tune?
Who was credited with writing the happy birthday tune on the copywright?
answer: Patty and Mildred J. Hill
Preston Ware Orem and Mrs. R. R. Forman
Natural Questions answer: Patty and Mildred J. Hill (from the Wikipedia article "Happy Birthday to You")