To elaborate on Bartok, to me, his string quartets are among the greatest works in that genre. Other 20th century string quartets to get are those of Shostakovich, the huge number of Villa Lobos quartets (some of the most overlooked works), and the quartets of Alwyn.
For choral works, there is a hybrid SACD/CD on the Chandos label, titled "Eternal Rest," that has terrific works by Mantyjarvi, Tichelli, Frank Martin, and Rene Clausen (all 20th century composers).
For choral works, there is a hybrid SACD/CD on the Chandos label, titled "Eternal Rest," that has terrific works by Mantyjarvi, Tichelli, Frank Martin, and Rene Clausen (all 20th century composers).