Critics and audiences assessing David Kellett's performances have consistently remarked on the clarity and purity of his tenor voice, praised the taste, refinement and subtlety of his interpretations and lauded his excellent diction in standard operatic, oratorio and recital repertoire. Reviewing David in David Amram's Twelfth Night, Bernard Holland of the New York Times wrote "Set apart from the rest of the cast was the pleasing, seamless tenor of David Kellett in the role of Feste."

David made his operatic debut as Count Belfiore in Mozart's La Finta Giardiniera with the Opera Shop at the Vineyard Theatre in New York City . He has appeared at the Lake George Opera Festival, the June Opera Festival, the Opera Festival of New Jersey and the Banff Centre for the Arts. Having performed over 45 principal and secondary roles in opera and operetta, he has portrayed several roles in some of the obscure Donizetti operas, including Daniele in Betly, Ernesto in Il Giovedi Grasso, and Eutropio in Belisario. David has also the distinction of having performed Count Almaviva in both the Rossini and Paisiello versions of Il Barbiere di Siviglia. His Mozart roles include Tamino in Die Zauberflöte, Belmonte in Die Entführung aus dem Seraglio, Don Ottavio in Don Giovanni, and Bastien in Bastien und Bastienne.

An active concert soloist, David has appeared at the Charles Ives Center for the Arts, with the Long Island Jewish Arts Festival, the Brooklyn Philharmonic, and the National Dance Institute under the baton of composer/conductor David Amram. As Mr. Amram's tenor of choice, David has sung in the composer's opera, Twelfth Night, and performed his songs in concert on numerous occasions. He appeared at Lincoln Center in 2007 on a program celebrating the 50th anniversary of Joseph Papp's Shakespeare Festival singing selections that were composed for productions directed by Papp during the first 11 years of its existence. His most recent orchestral appearance with Maestro Amram was the inaugural concert for the new Oskar Shindler Performing Arts Center in West Orange, New Jersey. He has also appeared with the Mid-Atlantic Chamber Orchestra, the Garden State Philharmonic, the Highlands Symphony Orchestra, the Long Island Jewish Arts Festival Orchestra, the Fairfield Chamber Orchestra, the Bridgeport Chamber Orchestra and the Princeton University Orchestra.

As an oratorio soloist, he has appeared with the Bach Concert Series in Baltimore, the Mendelssohn Choir of Connecticut, the Long Island Choral Society, the Monmouth Civic Chorus, the Oratorio Society of New Jersey, the Choral Arts Society of New Jersey, the Summit Chorale, the Richmond Choral Society in Staten Island, Commonwealth Opera, Concordia Chorale, the Arcadian Chorale, Ars Musica, the Putnam Chorale, the Glee Club and Chapel Choir at Princeton University, Concordia Collge in Bronxville, New York and numerous other organizations in the New York area. In recital, David has presented programs on the Illiade Concert Series in Strasbourg, France with pianist Masako Hayashi-Ebbesen, Smith College, Princeton University, Westminster Choir College, the Glen Ridge Concert Series and other venues in the New York area.

Recently turning to Early Music, David has sung the role of Eumaeus in Monteverdi's Return of Ulysses at Princeton University and concerts of Monteverdi & Cavalli opera excerpts, French Airs de Cours and vocal music of Claudio Sarcini and Barbara Strozzi with the New York Continuo Collective in New York City and at the Boston Early Music Festival in June of 2013. His forays into the music of Bach include performances of the B-minor Mass and Cantata 208 with Bach in Baltimore and he recently sang his first Evangelist in Johannespassion with the Concordia Chorale and Camerata. His Handel oratorio roles have included the tenor soloist in Samson, Judas Maccabaeus, Esther, Semele, Solomon and of course, Messiah. He has appeared multiple times with the Practioners of Musick and Les Agréments de Musique in the Princeton area. David recently appeared with Lewis Baratz's early music ensemble, La Fiocco, in a program entitled The Lion & The Lamb: The Jewish Baroque. He has appeared in masterclasses with the famous Italian baritone and Baroque specialist, Furio Zanasi, Emma Kirkby, Julianne Baird and Ellen Hargis.

His new music endeavors include the world premieres of several works by Peter Westergaard. In 2008 he sang in Westergaard's Alice in Wonderland under the auspices of the Center for Contemporary Opera at Symphony Space in NYC. He originated the role of Sebastian in his The Tempest with the Opera Festival of New Jersey and the roles of Stubbs and the Parsee in a concert version of his opera, Moby Dick which has been recorded by Albany Records. He also premiered Westergaard's cantata, To the Dark Lady, based on 5 Shakespearean sonnets for vocal quartet and percussion. He has presented new compositions by composer Webster Young in concert in New York City on several occasions and performed in the premiere of The Rime of the Ancient Mariner by Hollis Thoms for soprano, tenor, bass-baritone soloists and chamber orchestra in Anapolis, Maryland.

Radio audiences have heard him on WQXR's Listening Room, and WNCN's WNCN's Live including a recreation of Vittorio Giannini's radio opera, Blennerhassett. Recordings of his operatic performances have been broadcast on WKCR and WBAI in New York City.

In December of 1990, David appeared in Zoe Caldwell's production of A Christmas Carol at the Hudson Theatre on Broadway. This production featured Christopher Plummer, Richard Kiley, Jason Robards, Maureen Stapleton, Julie Harris, E.G. Marshall and Ms. Caldwell, and was the first dramatic presentation in the newly renovated structure. In 1991, he was invited back for a return engagement with Eli Wallach appearing as Scrooge.

Since 1995, David has taught private voice at Princeton University. He made his directing debut with the university production of Mozart's Magic Flute in 2002. Since that time he has directed Gilbert & Sullivan's Patience and Mozart's Marriage of Figaro, Benjamin Britten's Albert Herring, a double bill of Purcell's Dido and Aeneas and the American theatrically staged premiere of Jonathan Dove's Tobias and the Angel and three student thesis opera productions. He has appeared regularly with the Richardson Chamber Players, the resident chamber music ensemble of the university.

In 2005, David began his association with the Princeton Festival appearing as Pirelli in their debut performance of Sondheim's Sweeney Todd. Since that time, he has directed their young artist productions of Menotti's Old Maid and the Thief, Man of La Mancha, The Fantasticks and Three Penny Opera, presented audition master classes and served as vocal consultant.