I frequently use the Mode II Melismatic Alleluia from the PBC, but I have been looking for something more than just the simple psalm-tone for the verses. I recently stumbled on a Sarum Psalter that contains a set of "neums" that can be added ad lib. to the end of the Antiphons at the final repetition.

I sketched out settings for the Mode II, Mode IV, and Mode VIII Alleluias in PBC, but I have only so far set the Mode II in Gregorio: PDF and GABC code below.

A note on the verse and the pointing: For the opening intonation of the verse I chose the the neum that comes from the Alleluia: Dies Sanctificatus, the Alleluia in PBC, altered to end on the reciting tone, which continues through the solemn mediation (as in the Gospel Canticles). The psalm-tone continues on the tenor, until the simple cadence, to which is appended the Sarum 'neum'. The pointing of the intonation of the verse includes the possibility for up to three preparatory notes before the first 'principal' accent, which would fall on the opening melisma; e.g. a word such a "misereatur" would put "misere-" on the three preparatory notes, and "-atur" on the melisma. The opening melisma may be devided into three parts for a word such as "Dominus": "Do-" from the beginning thru SOL, "-mi-" on the clivis & porectus, and "-nus" on the final clivis (with episema). This is all easier to do, than to describe. The mediant and final cadences follow the rules given in the Antiphonale Romanum II.

GABC:

user-notes: Example Christmas Day Mass;
commentary: from Gregorian and Sarum sources;
annotation: II;
centering-scheme: english;
%fontsize: 12;
%spacing: vichi;
%font: GaramondPremierPro;
%width: 4.5;
%height: 11;
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(f3)AL(e)le(f)lu(hi~)ia.(i_h_/ig/g_f_) ij(,) (hv.hih./ef/h_f_/hv.ghe./hhh.fgwhf.) V/(::) (dr//dr//dr) Di(f_e_/fgwh!iv)(jiihi)es(i_h_) (,) san(h)cti(h)fi(h)ca(h)tus(h) il(h)lux(h)it(h) no(h)bis:(h.) (,) ve(h)ni(h)te(h) gen(h)tes,(h) et(h) a(h)do(hg)ra(hi)te(ir) Do(hi)mi(hr)num:(h.) *(:) qui(h)a(h) ho(h)di(h)e(h) de(h)scen(h)dit(h) lux(h) ma(h)gna(h) su(h)per(g) (er) ter(ef)ram.(f_fghv_GFEfg/hf./hvGFE/fgwhf.) (::)