Contralto Karen Esquivel was born in the U.S.A., of a Costa Rican mother and father of Mexican descent. She obtained her BME and Master's degree in Voice / Opera Theater at the University of Nebraska, a MM in Opera Production from Florida State University and her Doctorate in Voice Performance from the same institution.

Her experience covers performances in Music Theater to Opera to Oratorio. Esquivel performed as the contralto soloist in performances of Handel’s Messiah, Beethoven’s Ninth Symphony, Schubert’s Mass in C, Vivaldi’s Gloria, Dvorak’s Requiem, Pergolesi’s Magnificat, Falla’s El Amor Brujo, Stravinsky’s Les Noces, Duruflé Requiem, Rossini’s Stabat Mater, and Prokofiev’s Alexander Nevsky. Esquivel has performed the roles of Fillipyevna in Eugene Onegin, Dame Quickly in Falstaff, Orphée in Orphée et Euridice, Katisha in The Mikado, Baba in The Medium, Une Voix in Les Contes d’Hoffmann, the Sorceress in Dido and Aeneas, Servilla in the baroque intermezzo Il marito giocatore e la moglie bacchettona, Doña Sofía in the premiere of The Tango of the White Gardenia, Desirée & Madame Armfeldt in A little Night Music, Bloody Mary in South Pacific and Aunt Eller in Oklahoma!. Esquivel has participated in the Apprenticeship Programs of the Des Moines Metro Opera and the Santa Fe Opera, where she covered the role of Gaea in Strauss’s Daphne. She has enjoyed directing over 50 stage productions, from Baroque to Contemporary opera, as well as creating costume and set designs.

Since 1997 she has formed a duo with her husband, Costa Rican pianist/coach Gustavo Castro, with whom she has performed recitals in Costa Rica, Nicaragua, France and the USA.  With Dr. Castro, she has presented nationwide on the theme of Spanish Opera, which was her area of study for her published Doctoral treatise, “El Gato Montés: A Victim in Spain's Struggle to Establish A National Operatic Identity.”

She served as Director of the Compañía Lírica Nacional de Costa Rica and taught at the Universidad de Costa Rica, the Universidad Nacional, and founded, along with her husband, a project for the formation of young opera singers known as Opera Nova Costa Rica, providing lessons and performance opportunities through the presentation of recitals, scene programs and operas throughout Costa Rica, in an effort to bring opera to the community.  Esquivel currently serves on the Board of the Kenyan Classical Singers Organization, a program whose goal is to discover and support young, talented singers from Kenya and the National Opera Association.

Esquivel has taught Voice  at Florida State University, Albany State University, Valdosta State University and is currently a Senior Instructor of Voice and Director of the Opera Ensemble at the University of Oregon in Eugene, Oregon.