Schubert, Mendelssohn, and Brahms also wrote secular cantatas, the best known of which are Brahms's "Schicksalslied" and "Nänie". A few composers developed a cappella music, especially Bruckner, whose masses and motets startlingly juxtapose Renaissance counterpoint with chromatic harmony. Mendelssohn and Brahms also wrote significant a cappella motets. The amateur chorus (beginning chiefly as a social outlet) began to receive serious consideration as a compositional venue for the part-songs of Schubert, Schumann, Mendelssohn, Brahms, and others. These 'singing clubs' were often for women or men separately, and the music was typically in four-part (hence the name "part-song") and either a cappella or with simple instrumentation. At the same time, the Cecilian movement attempted a restoration of the pure Renaissance style in Catholic churches. 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 early modernist composers, such as Richard Strauss, Sergei Rachmaninoff and Max Reger, 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 shift constantly (his harmonically innovative "Verklärte Nacht" for strings dates from the same period). Ukrainian composer Mykola Leontovych explored new ways of harmonizing and arranging Ukrainian folk songs, producing masterpieces such as "Dudaryk" and "Shchedryk", the latter of which featured a four-note ostinato theme and became a popular Christmas carol known as Carol of the Bells after Peter J. Wilhousky translated it. 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 setting of Psalm 130 "De Profundis".