The Canadian Enclycolpedia say this about the "early" organ works of Healey Willan (1880-1968): With the music for organ one enters a different world. Here Willan was thoroughly at home and made a significant and lasting contribution. One work stands out: the monumental "Introduction, Passacaglia and Fugue" of 1916. It represents the culmination of Willan's first period of organ composition, which started ca 1906 with a Fantasia on 'Ad coenam agni.' The Preludes and Fugues in C minor and B minor and the "Epilogue" are the other major works from this period. While not exploring the possibilities of the instrument as searchingly as his masterpiece, they are idiomatic and very typical of their time. They combine an innate Englishness (with a Stanfordian flavour) and a European chromaticism that can be found in Reger and Karg-Elert. (Willan knew and played a few pieces by the latter, but it is doubtful he had heard much Reger at the time he was writing these pieces.)
The "Fugal Trilogy" was published by Oxford University Press in 1958, and while a late work, seems to hearken back to Willan's earlier, "darkly German romantic style". Each of the three works in the set is essentially a "prelude and fugue", and each one explores a different "style" or "type" of setting.
The first movement, "Chorale and Fugue" shows the composer at his MOST Germanic! The opening chorale, "Sei gegrusset, Jesu gutig" is harmonized in the MOST Bach-like style that you can imagine. The fugue that follows is the largest single movement in the entire opus, and builds up through a fine contrapuntal working to a tremendous Reger-like conclusion, with the subject appearing on The Solo Tuba in the tenor register.