Constance Loudon Mellen was an arts administrator, costume designer, visual artist, and writer heavily involved with Washington D.C.’s classical music community. She was a founding member of the Opera Society of Washington (later the Washington Opera in 1977 and Washington National Opera in 2004) serving as Artistic Administrator and later as a Vice President of the Board of Directors. She helped found the Friends of Music of the Smithsonian and was integral in the creation and administration of the Smithsonian Friends of Music Musical Weekend from its inaugural weekend in 1972 to 1991.

Mellen was prolific as a costume designer and author. She designed costumes for 17 operas for the Opera Society of Washington between 1960-1967, many of which were later rented for use by companies such as the Santa Fe Opera and the Juilliard Opera Theater. Notably, Mellen designed and costumed over 200 performers for the world premiere of "Be Glad Then, America," an original opera composed by Pulitzer Prize winner John La Montaine and commissioned by the Pennsylvania State University Institute for the Arts and Humanistic Studies to commemorate the United States Bicentennial in 1976.