20th-century choral music mixes several varied styles, often within the same piece. Composers were not expected to conform to one specific music texture or feel, as had been the case in previous musical periods.
Much of choral music from the 1900s, especially from the latter half of the century, is not restricted to the conventional eight-tone scale that Western music had been based on for centuries. Many composers experimented with alternate scales and quarter-tones.
Unlike baroque and classical choral music, 20th-century choral pieces change time signature frequently, often measure by measure. This makes for a unique rhythmic feel and adds excitement and interest to the piece. Some examples of more modern music don't even use a time signature.
Tempo in more modern music is much freer and varies quite often. Dynamics do the same, and to higher extremes, including whispering and shouting.
Twentieth-century choral music makes use of the human voice in many more ways than just for singing words. Many pieces include numerous nonsinging vocal sound effects.