The following are some of de Guzman's contributions to the music world:
Teaching: De Guzman was a highly respected music teacher and educator. He taught at the University of the Philippines Conservatory of Music and the Centro Escolar University Conservatory of Music. He also founded the Philippine School of Music.
Composition: De Guzman composed over 100 works, including operas, zarzuelas, songs, and instrumental pieces. His most famous work is the opera "Dalagang Filipina" (Filipina Maiden), which was first performed in 1917.
Music theory: De Guzman wrote several books and articles on music theory. His most important work is the "Teoría de la música" (Theory of Music), which was first published in 1922.
Promotion of Filipino music: De Guzman was a strong advocate for Filipino music and culture. He helped to promote and preserve traditional Filipino music and to develop a new style of Filipino music that was influenced by Western classical music.
Awards and honors: De Guzman received numerous awards and honors for his contributions to music. He was awarded the National Artist of the Philippines for Music in 1973.
Constancio de Guzman is considered one of the most important figures in Philippine music history. His work helped to shape the development of Filipino music and to promote it around the world.