In the Orgelbüchlein Bach set out to compose a prelude based on each of the 164 chorales then in common use. Each page of the manuscript was inscribed with the title of a chorale but only 46 were completed. The Orgelbüchlein Project aims to fill the gaps by providing preludes based on the remaining chorales; some have been commissioned, and others have been submitted. Paul Ritchie\’s setting of \’Ach Gott, erhör\’ mein Seufzen\’ has been added to the collection and may be downloaded for free by clicking on this link, scrolling down to number 105, and clicking on the name Paul Ritchie in brown type.