The following is paragraph CLXXIII (173) of the Chanson de Roland, verses 2338 to 2354

Among the Anglo-Norman characteristics the most noticeable are:

The phonetics

- /ei/ result of the diphthonging of /e/ closed free tonic or of /e/ followed by /y/: freindrat , seint , veit , Franceis
- /e/ corresponding to the diphthong /ie/ in Old French: chevaler , destrer
- /o/ closed Latin, free or blocked, where the monotonic /o/ is usually written u: cuntre , cum
- /o/ open free tonic is usually written oe: aproeciez .
For consonants we can note:
- The intervocalic d is maintained in the final letter: ad
- The usual keeping of the letter l before a consonant: Mult , dulcement
- The sporadic keeping of k before an a: Carles

Archaisms

The old [au] diphthong

These are words where the spelling -au- corresponds in the use of modern French to the pronunciation [o]

Evolution : in the old "langue d'oïl" there was, since the 11^th century, a very common diphthong, [au] which came from a Latin [a] followed by a [l] in front of another consonant. Little by little this [au] opened in [ao], this pronunciation was very much alive in French at the end of the 15^th century. From the next century the diphthong became [o] but the French spelling continued until today to write this simple vowel -au- .

On the text above examples such as enchalcet or Rencesvals show the use of the proto-form -al- which later became -au-

The old [eau] triphthong

Similarly to the previous diphthong, there was during the Middle Ages a triphthong [eau] which came from the evolution of an old brief e from Latin followed by a l in front of another consonant (eg [wezeau] for oiseaux -birds- from the Latin aucellos ). In a similar fashion as before the last element of the triphthong opened as time went by giving [eao]. From the 13^th century, the first element of this triphthong tended to close more, thus the pronounciation became [iao] or [jao] among the people of Normandy. However by the end of the 16^th century the triphthong became [o] as it is pronounced nowadays. Again, in spite of the changes, the spelling -eau- has been kept.

The [we] combination

It is one of the most common phenomenons throughout the "langue d'oïl" dominions. Moreover, in order to "sound like a peasant" in French it is quite common to transform here and there all the [wa] of the French language into [we]. In fact this replacement is not always justified.

Evolution : The spoken forms of the "langue d'oïl" as for the French itself until the end of the 18^th century have had the [we] combination in several words. To simplify, we can say that this combination has two different origins: the evolution of a Latin e in a certain position and of a Latin o followed by a yod ( [i] or [j] ). The latter could have been formed by an ancient [k]. The first case does not concern the spoken forms of the western "langue d'oïl". However the situation has been the same all over the territories of the "langue d'oïl" dominions for the second case. The [o + i] has evolved has evolved between the 7^th and the 13^th century as follows: [oi] > [oe] > [we]. The [we] combination has therefore been very much alive for a long period of time. It has however been in competition with the [wa] pronunciation which eventually won over, at least in Paris and in the French language for many provinces have kept in their local speeches the old pronunciation.
As before we can note that the old spelling -oi- has been kept throughout over 900 years of pronunciation changes.

Further Information:

Marie de France, that is from Île-de-France ("Marie ai nun, si sui de France"), had lived in England at the court of Henry II Plantagenet (1154-1189), duke of Normandy, count of Anjou, duke of Aquitaine and... husband of Eleanor! Her text is strongly coloured by one of the most significant scripta after Picard and Lorrain: Anglo-Norman.

"Mult* unt* esté noble barun* cil de Bretagne, li Bretun*.
Jadis suleient par pruësce*, par curteisie* e par noblesce
des aventures que oeient*, ki a plusurs* genz aveneient,
faire les lais pur* remembrance, qu'um* nes* meïst en ubliance.
Un en firent, ceo* oï cunter*, ki ne fet mie a ublïer*."
(Lais : Equitan)

Those were very noble barons, the lords of Brittany, the Bretons.
They had in ancient times a custom that proved their valour,
their courtesy and their nobility: when they intended to tell their adventures
which happened around them they had a Lais being composed
to preserve its memory, to prevent it from falling into oblivion.
They have composed one which I've heard myself
and deserves well not to be forgotten.
(Translation in English by Jean-Loup Rebours from the French translation by Laurence Harf-Lancener in Histoire Médiévale)

Anglo-Norman features:
(o)un for on: unt (ont[have]), barun (baron), Bretun (Breton), cunter (conter[tell])
ei for oi : suleient (soloient/souloient [only]); curteisie (cortoisie [curtesy]); oeient (oioient); aveneient (avenoient = advenoient [happened to])
ceo for"ce" [that/this] neural demonstrative pronoun
u not only represents the sound[u] as in francian but also [ou] in front of a nasal consonant (n or m) : um (on [impersonal "we"]), personal pronoun at the third person originating from the noun homme, "uem" ,"om" (man), but not only : pruësce (proesse [valour, bravery]), suleient (soloient), curteisie (cortoisie), plusurs (plusor [many]), pur (por [for]), ubliance (obliance [oblivion]), ublïer (oblïer).
Typical features of ancient French : nes is the contraction of ne + les .

Bibliography:

La chanson de Guillaume (Classiques Garnier, Editions Bordas - 1991)
La chanson de Roland (Editions Folio Classique - 2001, first edition 1979)
Oyez ke dit Marie, Etude sur les Lais de Marie de France by Claude-Henry Joubert (Librairie José Corti - 1987)
La Normandie Dialectale by René Lepelley (Presses Universitaires de Caen - 1999)
Histoire Médiévale issue No 13 (Editions Harnois - 2001)