I hardly ever have linked to music by Johannes Brahms but he's one of the 19th century composers whose music I do like (and Scott Joplin, of course).
This is a choral prelude and fugue on one of the more famous Lutheran hymns for Holy Saturday.
This video features a score to read along with as you hear the performance and the choral tune shows up in the prelude with text above the melody so you can identify the chorale when it appears in the big chunky bass pedals solo throughout the fugue. Once the chorale tune has been traversed the fugue is over, whose subjects and countersubjects are loosely inspired by and fit with the hymn tune without being quotations of it.
