William Richard Cumpiano (born April 30, 1945) is a builder of stringed musical instruments and is known for his writing and teaching of the art of luthiery.

[5] Among his customers are Arlo Guthrie, Michael Lorimer, John Abercrombie, Country Joe MacDonald, the Todd Rundgren band, June Millington, and Joel Zoss.

[4] Cumpiano has taught his craft for over twenty years out of his studio, in schools, during workshops and lectures and through numerous publications.

Cumpiano met Juan Sotomayor, a prize-winning photographer who worked on the New York Times staff.

In 1992, he co-founded "The Puerto Rican Cuatro Project" with Juan Sotomayor and Wilfredo Echevarría, an expert in media communications.

The Cuatro Project is also dedicated to promoting and preserving the Puerto Rican décima verse form and the traditional song as created by its greatest troubadours, living and past.

[6] Cumpiano, who is also a founding board member and president of the Association of Stringed Instrument Artisans (ASIA), has lectured about his skills at conventions of the Guild of American Luthiers (GAL).

Cumpiano, together with Sotomayor and Echevarría, wrote, directed and produced twoDVD documentaries for The Cuatro Project.

Cumpiano and cultural researcher David Morales produced another DVD documentary THE DÉCIMA BORINQUEÑA: An Ancient Poetic Singing Tradition, directed by Myriam Fuentes.

[11] Cumpiano is putting the finishing touches on the manuscript of "The Cuatro Project", which he and his comrades began fifteen years ago, tracing the roots and evolution of Puerto Rican traditional stringed instruments.