So had he been writing in English, Bach might have named the piece Trio [based] on [the 1524 Lutheran chorale] "Nun komm der Heiden Heiland." There is nothing special about the fact that your examples are pieces for (solo) organ; the principle of using [genre name] + "on" + [a t...
which is festive Christmas music streets above all the rest; Part 2, with that miraculous double ofUnd es warenHirtenwith the soul-stirringBrich an, o schones Morgenlichtchorale to follow; then a rush to Part 5 and the bouncy joy of its openingEhre sei dir, Gott, gesungenchorus; and Part...