Yes.
According to United States copyright law in United States Code, Title 17 §106, authors of works such as musical compositions have the exclusive right 'to perform the copyrighted work publicly.' In United States Code, Title 17 §101, the law defines publicly performing a work as 'to perform or display it at a place open to the public or at any place where a substantial number of persons outside of a normal circle of a family and its social acquaintances is gathered.'
This means that if you sing Happy Birthday to your family at home, you're probably not committing copyright infringment. However, if you do it in an restaurant — and if the restaurant hasn't already worked out a deal with ASCAP — you may be engaging in copyright infringement."
