Is there a law that mandates a specific manner of singing the Philippine National Anthem, and if so, is it mandatory or merely a directory?

Schoolkids sang the Philippines' national anthem for Filipino language week in New Zealand. Footage shows the youngsters and teachers gathered at the school grounds where Lupang Hinirang was ...

The tradition of performing the anthem took off because people ... the national anthem is typically played only before international competitions.) Promising young vocalists sing it at local ...