As in other genres of music, choral music underwent a period of experimentation and development during the 20th century. While few well-known composers focused primarily on choral music, most significant composers of the early century produced some fine examples that have entered the repertoire.
The late-Romantic composers, such as Richard Strauss and Sergei Rachmaninoff, contributed to the genre. Ralph Vaughan Williams's Mass in G minor harks back to the Renaissance style while exhibiting the vibrancy of new harmonic languages. Vaughan Williams also arranged English and Scottish folk songs. Arnold Schoenberg's Friede auf Erden is a tonal kaleidoscope, whose tonal centers are constantly shifting.
At the end of the 19th century and the start of the twentieth, male voice choirs became popular with the coal miners of South Wales, and numerous choirs were established including the Treorchy Male Choir, Morriston Orpheus Choir and Cor Meibion Pontypridd Male voice choirs. Although the mining communities which gave rise to these choirs largely died out in the 1970s and 1980s with the decline of the Welsh coal industry, many of these choirs continue, and are seen as a traditional part of Welsh culture and perform Worldwide.
The advent of atonality and other non-traditional harmonic systems and techniques in the 20th century also affected choral music. Serial music is represented by choral works by Arnold Schoenberg, including the anthem "Dreimal Tausend Jahre," while the composer's signature use of sprechstimme is evident in his psalm "De Profundis." Paul Hindemith's distinctive modal language is represented by both his a cappella Mass and his Six Chansons on texts by Rilke, while a more contrapuntally dissonant style comes through in his secular requiem, When Lilacs Last in the Dooryard Bloom'd. Olivier Messiaen also demonstrates dissonant counterpoint in his Cinq Rechants, which tell the Tristan and Isolde story. Charles Ives' psalm settings exemplify the composer's incomparably radical harmonic language. Tone clusters and aleatory elements play a prominent role in the choral music of Krzysztof Penderecki, who wrote the St. Luke Passio, and Gyorgy Ligeti, who wrote both a Requiem and a separate Lux Aeterna. Milton Babbitt incorporated integral serialism into works for children's chorus, while Daniel Pinkham wrote for choir and electronic tape. Meredith Monk's Panda Chant and Astronaut Anthem explore overtones in an unconventional text setting.
A primitivist approach is exemplified by Carl Orff's widely performed Carmina Burana. In the United States, Aaron Copland, Samuel Barber, and Randall Thompson wrote signature American pieces. In Eastern Europe, Béla Bartók and Zoltán Kodály wrote a small amount of music for choirs. Frank Martin's Mass for double choir combines modality and allusion to Medieval and Renaissance forms with a distinctly modern harmonic language and has become the composer's most performed work.
American minimalism and post minimalism are represented by Steve Reich's Desert Music, choral excerpts from Philip Glass's Einstein on the Beach and John Adams' The Death of Klinghoffer, and David Lang's Pulitzer Prize-winning Little Match Girl Passion.
During the mid 20th century, barbershop quartets began experimenting with combining larger ensembles together into choruses which sing barbershop music in 4 parts, often with staging, choreography and costumes. The first international barbershop chorus contest was held in 1953 and continues to this day.
During the late 20th century, one of the major areas of growth in the choral movement[citation needed] has been in the areas of LGBT choruses. Starting around 1979, gay men's choruses were founded within a period of months in major U.S. cities such as New York, Los Angeles, Seattle and Dallas. Over the last quarter century the number of such groups, men's, women's and mixed, has exploded.
At the turn of the 21st century, choral music has received a resurgence of interest partly due to a renewed interest in accessible choral idioms. Multi-cultural influences are found in Osvaldo Golijov's St. Mark Passion, which melds the Bach-style passion form with Latin American street music, and Chen Yi's Chinese Myths Cantata melds atonal idioms with traditional Chinese melodies played on traditional Chinese instruments. Some composers began to earn their reputation based first and foremost on their choral output, with the highly popular John Rutter, Morten Lauridsen, and Eric Whitacre being three of the most well-known examples. The large scale dramatic works of Karl Jenkins seem to hearken back to the theatricality of Orff, and the music of James MacMillan continues the tradition of boundary-pushing choral works from the United Kingdom begun by Britten, Walton, and Leighton. Meanwhile, prominent primarily orchestral composers such as Augusta Read Thomas, Sofia Gubaidulina, Aaron Jay Kernis, and Thomas Ades still contribute vital additions to the choral repertoire.