66. Medial groups may be conveniently classified as follows:—A. Double Consonants (1); B. Groups of Dissimilar Consonants: groups ending in l (2), groups ending in r (3), groups ending in w (4), groups ending in y (5), groups beginning with l, m, n, r, or s and not ending in l, r, w, or y (6), all other groups (7). This order will be followed.[57]
1. It should be noted that the prefixes ad-, sub- regularly assimilate their d or b to the following consonant: ✱ad-rīpāre ＞ arribar, sub-venīre ＞ sovenir. Sosrire, sosterrar, sostraire show a substitution of prefix, due, no doubt, to the analogy of sospirar, sostener.
1. Double Consonants.
67. In general, the double consonants became single, in the 9th or 10th century (perhaps earlier before the accent), but underwent no other change save those described in §§ [63], [64]: abbātem ＞ abat, sĭccum ＞ sẹc, rĕddo ＞ ręt, affībulāre ＞ afiblar, aggregāre ＞ agregar, flamma ＞ flama, pĭnna ＞ pẹna, cappa ＞ capa, passum ＞ pas,[58] mŭttum ＞ mọt, advenīre ✱avvenīre ＞ avenir.
(1) Cc before a, in the east and northeast, became tš; elsewhere, c; bŭcca ＞ bọca bọcha, vacca ＞ vaca vacha.
(2) Ll, in some southern dialects, became l´; elsewhere, l: capĭllum ＞ cabẹl cabẹlh, grȳllum ＞ gril grilh, mantĕllum ＞ mantęl mantęlh, villānus ＞ vilas vilhas. It is possible, however, that -llī regularly became l´ in Limousin, while ll before other vowels was not palatalized: caballum ＞ caval, caballī ＞ cavalh; ĭllī ＞ ilh, ĭllōs ＞ ẹls; this would account in part for the frequent occurrence of lh in the poems. So in some dialects -nnī ＞ n´: annī ＞ anh. Cf. § [51], 1. For final ls and l, see § [65], L: ĭllos ＞ ẹls ẹus, vallem ＞ val vau. For Gascon l ＞ r, see § [10]: appĕllat ＞ apęla apęra.
(3) Rr, when intervocalic, seems generally to have been distinguished from r during the literary period and later: cŭrrĕre ＞ cọrre, ✱corrŭptiāre ＞ corrossar, errāre ＞ errar, tĕrra ＞ tęrra. Occasionally, however, rr is found in rhyme with r.
2. Groups Ending in L.
68. The groups of two consonants will be treated in alphabetical order. It will be seen that bl, rl, sl remained unchanged; ml developed a glide consonant between its two members; pl, tl, βl and yl respectively voiced, assimilated, and vocalized their first element; while cl, gl were fused into l´. For an explanation of this last phenomenon, see § [79].
Bl ＞ bl: nĕbŭla ＞ nębla, ✱oblītāre ＞ oblidar, sabulōnem ＞ sablọn.[59]