Here's a version of the preface for Advent. I did it because it's not in our Missal and the priest wanted to sing it. Can't guarantee it's 100% authentic - probably merits a bit of re-work, particularly the long monotonic phrases.

% !TEX TS-program = gregorio
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(c3)Ve(f)re(h) di(h)gnum(h) et(h) iu(h)stum(h) est,(h) (,)
æ(h)quum(h) et(h) sa(h)lu(gf)tá(fg)re,(g) (;)
nos(f) ti(h)bi(h) sem(h)per(h) et(h) u(h)bí(h)que(h) (,)
grá(h)ti(g)as(gf) á(fg)ge(g)re:(g) (;)
Dó(f)mi(h)ne,(h) san(h)cte(h) Pa(h)ter,(h)
om(h)ní(h)po(h)tens(h) æ(h)tér(h)ne(gf) De(fg)us:(g) (;)
per(g) Chri(f!gwh)stum(g) Dó(fe)mi(ef)num(g) no(fg)strum.(f) (:)
Quem(f) pér(h)di(h)to(h) hó(h)mi(h)num(h) gé(h)ne(h)ri(h) (;)
Sal(h)va(h)tó(h)rem(h) mi(h)sér(h)i(h)cors(h)
et(h) fi(h)dé(h)lis(h) pro(h)mis(gf)sí(fg)sti:(g) (;)
cu(f)ius(h) vé(h)ri(h)tas(h) in(h)strú(h)e(h)ret(h) ín(h)sci(h)os,(h)
sán(h)cti(h)tas(h) iu(h)sti(h)fi(h)cár(h)et(h) ím(h)pi(h)os,(h) (;)
vir(h)tus(h) ad(h)iu(h)vár(h)et(h) in(gf)fír(fg)mos.(g) (;)
Dum(f) er(h)go(h) pro(h)pe(h) est(h) (,)
ut(h) vén(h)i(h)at(h) quem(h) mis(gf)súr(fg)us(g) es,(g) (;)
et(f) di(g)es(g) af(g)fúl(g)get(g) li(g)ber(g)a(g)ti(g)ón(g)is(g) nos(g)træ,(g) (;)
in(g) hac(g) pro(g)mis(g)si(g)ó(g)num(g) tu(g)á(g)rum(g) fi(h)de,(g) (;)
pi(g)is(g) gáu(g)di(g)is(fe) ex(ef)sul(g)tá(fg)mus.(f) (;)
Et(f) í(ef)de(f)o(f) (,) cum(f) Án(h)ge(h)lis(h) et(h) Ar(gf)chán(fg)ge(g)lis,(g) (;)
cum(f) Thro(h)nis(h) et(h) Do(h)mi(h)na(h)ti(gf)ó(fg)ni(g)bus,(g) (;)
cum(f)que(h) om(h)ni(h) mi(h)lí(h)ti(h)a(h) cæ(h)lés(h)tis(g) ex(gf)ér(fg)ci(g)tus,(g) (;)
hym(f)num(h) gló(h)ri(h)æ(h) tu(h)æ(gf) cá(fg)ni(g)mus,(g) (;)
si(f!gwh)ne(g) fi(fe)ne(ef) di(g)cén(fg)tes:(f) (::)