On May 5, 1960, Allen began her long partnership with Bernstein and the New York Philharmonic in a concert performance of
Four Saints in Three Acts. She was a regular guest artist with the orchestra through 1975, appearing as a soloist in performances of such works as
Johann Sebastian Bach's
Johannes Passion, Bach's
St Matthew Passion, Bach's
Ich elender Mensch, wer wird mich erlösen,
Beethoven's
Symphony No. 9,
Berg's
Four Songs, Op. 2, both of Berg's settings of
Theodor Storm's
Schliesse mir die Augen beide,
Joseph Haydn's
She Never Told Her Love,
Liszt's
Die Legende von der heiligen Elisabeth,
Mahler's
Lieder eines fahrenden Gesellen, Mahler's
Symphony No. 3, Mahler's
Symphony No. 8,
Franz Schubert's
Die junge Nonne, Schubert's
Erlkönig, Schubert's
Winterreise,
Stravinsky's
A Sermon, a Narrative and a Prayer, and
The Star-Spangled Banner among others. After an eleven-year absence she returned for one last performance with the orchestra in 1986. In 1961 Allen sang Teresa to the Amina of
Joan Sutherland in the
American Opera Society's production of
La sonnambula at Carnegie Hall. She performed with the AOS again the following year as Baba the Turk in Stravinsky's ''
The Rake's Progress'' with
Alexander Young as Tom Rakewell,
John Reardon as Nick Shadow, and
Judith Raskin as Anne Trulove. She sang the role of Armando di Gondì in
Gaetano Donizetti's
Maria di Rohan with the AOS in February 1963 with
Ilva Ligabue in the title role and
Lino Puglisi as Enrico. In March 1963 she sang Juno in Handel's
Semele with conductor
Johannes Somary and the
Amor Artis choir and orchestra. Soprano
Helen Boatwright was in the title role,
Donald Gramm sang Cadmus and Somnus, and
Blake Stern was Jupiter. She returned to AOS again in 1965 to sing Zaida in
Rossini's
Il turco in Italia with
Giorgio Tadeo as Selim, Judith Raskin as Fiorilla,
Elfego Esparza as Don Geronio,
Jerold Siena as Narciso, and
Sherrill Milnes as Prosdocimo. That year she also portrayed Clitemnestre in
Gluck's
Iphigénie en Aulide at the AOS with
Christa Ludwig in the title role,
Richard Cassilly as Achille, and
Walter Berry as Agamemnon. Allen appeared in two operas at the Midsummer Musical Festival at
Philharmonic Hall in the summer of 1963. In July she sang Annio in
Mozart's
La clemenza di Tito under the baton of
Paul Callaway. Also in the cast were
Martina Arroyo as Vitellia,
David Lloyd as Titus,
Beverly Wolff as Sextus,
Margaret Kalil as Servilia, and
David Clatworthy as Publius. In August Allen portrayed the Female Chorus in
Benjamin Britten's
The Rape of Lucretia with
Lili Chookasian in the title role,
William Greene as the Male Chorus,
Joan Caplan as Bianca,
Joan Gavoorian as Lucia,
Ara Berberian as Collatinus, David Clatworthy as Tarquinius, and
Ron Bottcher as Junius. Allen had a major triumph in 1964 as Jocasta in
Stravinsky's
Oedipus Rex at the
Teatro Colón in
Buenos Aires. She made her
San Francisco Opera debut two years later as Azucena in
Il trovatore with
McHenry Boatwright as the Count di Luna, later reprising that role with the company in 1971. Engagements soon followed at the
Canadian Opera Company (1971), the
Palacio de Bellas Artes (1971), and the
Washington National Opera (1972). She was committed to the New York City Opera from 1973 to 1975 where her roles included Azucena, Mistress Quickly in
Falstaff, Jocasta in
Oedipus rex, and Eurycleia in ''
Il ritorno d'Ulisse in patria''. At the
Santa Fe Opera Allen sang Pythia in
Aribert Reimann's
Melusine and Genevieve in
Claude Debussy's
Pelléas et Mélisande in 1972. She returned to that house in 1975 to portray Mistress Quickly and the grandmother in
Manuel de Falla's
La vida breve. She made her debut at the
Metropolitan Opera as the Commère on February 20, 1973, in a cast that included
Clamma Dale as St. Teresa I,
David Britton as St. Stephen, and
Barbara Hendricks as St. Settlement. She was invited to sing at Mexico´s city for Casals´hommage in The Manger. In 1975 she sang Monisha in the first fully staged production of
Scott Joplin’s
Treemonisha at the
Houston Grand Opera. She portrayed the role again in the Fall of 1975 at the
Kennedy Center and in 1976 in New York City. Other roles in her repertoire included Sesto in
La Clemenza di Tito, the Sorceress in
Dido and Aeneas, and Ulrica in Verdi's
Un ballo in maschera. Allen was also highly active internationally as a concert singer and recitalist during the 1960s and 1970s. She made appearances at the
Caramoor,
Casals,
Cincinnati May,
Marlboro,
Ravinia,
Saratoga, and
Tanglewood Music Festivals. She appeared with a number of notable orchestras including the
Philadelphia Orchestra and the
American,
Boston,
Chicago, and
Cincinnati symphony orchestras to name just a few. Her concert work led to collaborations with such conductors as
Pierre Boulez,
Pablo Casals,
Edo de Waart,
Antal Doráti,
István Kertész,
Rafael Kubelík,
Erich Leinsdorf,
Lorin Maazel,
Charles Munch,
Eugene Ormandy,
Seiji Ozawa,
Georg Solti,
Leopold Stokowski and
Enrique Gimeno. She also appeared in recitals throughout North and South America, Europe, and Asia. ==Later life and career==