Markull's chorale preludes of Op. 123 are the well considered fruit of a lifetime's experience of leading worship from a great organ in an enormous space. This collection was published in 1880 with the title 24 Chorale Preludes and Ornamented Chorales, Based on the Most Beautiful and Most Useful Hymn Tunes for use in Worship, for Experienced Organists.Markull intended this opus as his Orgelbüchlein--a distillation of 60 years of chorale improvisation. It is a catalog of his compositional technique, formally rooted in late Baroque and Classical tradition, yet reflecting the musical sensibilities of his time. A stoplist of the organ used by Markull (in the main nave Anthoni organ in 1760 after the modification by F.R.Dalitz) is provided to grant a further understanding of the registrations selected or to suggest other appropriate options. Of course, these chorales will appear in other hymnals, but the exact hymn nubers are provided for the Evangelical Lutheran Worship and the Lutheran Service Book.