Amongst former pupils of Babbitt, Westergaard stands out for his contributions to serial theory, as well as for his compositions, which are characterized by a delight in symmetry and mirror relationships, together with a concern for the systematic and integrated use of all the parameters of music, producing multileveled, clear, beautiful, and audible patterns (Griffiths 1981, 160–61).
Music
Operas
Charivari (1953)
Mr. and Mrs. Discobbolos (1966)
The Tempest (1994)
Chicken-Little (1997)
Moby Dick: Scenes from an Imaginary Opera (2004)
Alice in Wonderland (2006)
Film version of Alice in Wonderland published by Albany records.[full citation needed]
Vocal music
Cantata I: "The Plot Against the Giant" (text: W. Stevens), for female voices, clarinet, harp, and cello (1956)
Cantata II: "A Refusal to Mourn the Death, by Fire, of a Child in London" (text: Dylan Thomas), for bass and ten instruments (1958)
Cantata III: "Leda and the Swan" (text: William Butler Yeats), for mezzo-soprano, clarinet, viola, vibraphone, and marimba (1961)
Cantata IV: "Spring and Fall: To a Young Child" (text: Gerard Manley Hopkins), for soprano and five instruments (1964)
There Was a Little Man for soprano and violin (1979)
Ariel Music (text: William Shakespeare, from The Tempest), for soprano and ten instruments (1987)
Ode (text: Ben Jonson), for soprano, flute, clarinet, harp, violin, and viola (1989)
anyone lived in a pretty how town (text: E. E. Cummings), for SATB choir (1997)
Cantata V: "'Byzantium' and 'Sailing to Byzantium'" (text: William Butler Yeats), for baritone and percussion quartet (1997)
There Was a Lady Loved a Sow (text: traditional) (1997)
Cantata VI: "To the Dark Lady" (text: William Shakespeare), for soprano, mezzo-soprano, tenor, baritone, and percussion duo (1999)
Instrumental music
String Quartet, 1957;
Five Movements, for small orchestra (1958)
Quartet, for clarinet, vibraphone, violin, and cello (1960)
Trio, for flute, cello, and piano (1962)
Variations for Six Players, for flute, clarinet, piano, percussion, violin, and cello (1963)
Divertimento on Discobbolic Fragments, for flute and piano (1967)
Noises, Sounds, and Sweet Airs, for ensemble (1968)
Griffiths, Paul. 1981. Modern Music: The Avant Garde since 1945. New York: George Braziller. ISBN0-8076-1018-6.
Pratt, Michael J. 2001. "Westergaard, Peter (Talbot)". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.