He played the trombone in cabarets and circuses, and later worked as an assistant conductor of the Nueva Ecija High School Orchestra, where he started composing music.

Much later, he continued his studies under Vittorio Giannini at the Juilliard School in New York, U.S.[2] De Leon married pianist Iluminada Mendoza with whom he had six children, including Bayani, a prominent composer, and Felipe Jr., a writer.

[5] Being affected by the said movement, De Leon, along with his fellow composer Lucio San Pedro, continued the nationalist tradition of Antonio Molina, Francisco Santiago, and Nicanor Abelardo by using the material from Filipino folk songs as the basis of their own created compositions.

[6] After independence, De Leon soon composed the symphonic poems, "The Cry of Balintawak" and "Bataan" to commemorate the Filipinos who suffered under the Japanese occupation.

In exchange, De Leon composed for the vice president two symphonic poem during his stay at the Lopez estate in Iloilo, Philippines namely Roca Encantanda and Siete Pecados.