Sounds and spelling

in Early Middle English (eME)

Comparing Early Middle English (eME) to Modern English (ModE), we note these key differences:

ModE usually represents long vowels with a pair of letter, e.g. ee, oo, oa, whereas in eME, long vowels are indicated by a single letter with a short stroke (or diacritic) above it - e.g. e__, o__, a__;
eME long vowels are long versions of the corresponding short vowels - in other words, e__ is essentially a doubled e; the same is not true of ModE however - ee does not sound like a drawn-out e;
some eME sounds no longer exist in ModE¹ - long o__ and e__, as well as g and h in the middle or at the end of a word (/o:/,/e:/,/G``/,/x/ respectively);
some letters used in eME are no longer used in ModE - y%, t`, ae;
some letters used in ModE are rarely used in eME, and generally only in words borrowed from French, Latin or Greek - j, qu, v, and z.

Short Vowels

eME short vowels e, i and o /E`/ /I`/ /O`/ - are pronounced the same way as in ModE pet, pit and pot²;
eME a /a/ - is like a short version of a in ModE father, or the short a of Scottish man, or the a of Italian and Spanish; it is not the a /ae/ in ModE cat and man, as it's generally pronounced in southern England, North America and Australasia.
eME u /u/ - is always as in ModE full or put, never as in ModE but.

Long Vowels

a__ /a:/ - like the a in ModE father; perhaps a little further forward towards the sound in four, like the a of South African car;
e__ /e:/ - like the ea in great or the a in take; but hold the initial sound without letting it slide into an i; this is not a diphthong; in fact the sound doesn't exist in standard modE; it does exist however in the Scottish pronunciation of great and take; you'll also find it in Italian - closed e (bene) and in French - e acute (liberté);
i__ /i:/ - like the i in machine (not the i in bike);
o__ /o:/ - like the o in whole; but hold the initial sound without letting it slide into a u; this is not a diphthong; in fact the sound doesn't exist in standard modE; it does however in the Scottish pronunciation of whole and Oh!, for example; you'll also find it in Italian - closed o (o sole mio) and in French - o circumflex (rôle); alternatively try singing o sole mio in operatic fashion and note the shape of your lips - rounded;
u__ /u:/ - like the oo in fool or the ou in group or boudoir - but make sure your lips are rounded (which will come naturally if you're from the North of England or the "Celtic fringe");
ae /E`:/ - like the ea in pear and yeah (not the ea in leap or great);

Consonants

In general, consonants are pronounced as in ModE. However note the following:

h in the middle or at the end of a word, is pronounced like the ch in Scots loch - /x/ or licht - /C``/; e.g. burh /bu:rx/ and niht /niC``t/;
g in the middle of a word, also has a sound which no longer exists in ModE - /G``/; e.g. agene, fugel; to make this sound, do a very quick gargle; note this is the same sound the Dutch make with the G of Van Gogh;
the y sound in ModE year is spelt with a letter which no longer exists in ModE - y%, called insular g; e.g y%aer /jE`:r/;⁶
the th sound in ModE this and thin is spelt with a letter which no longer exists in ModE - t`, called thorn; e.g t`is /T``is/; note that t` was always pronounced like th in ModE thin, at the beginning of a word;
the sh sound in ModE ship is spelt in eME with the letter combination sc; e.g scip scal sco__ /S`ip S`al S`o:/;
the sk sound in school and Scot is always spelt sk in eME, e.g. sko__l Skot /sko:l skO`t/;
the v sound in ModE loves is spelt in eME with the letter f; e.g lufet` /luv@`T``/; the letter <v> is not used³; note - f is always pronounced /v/ between vowels⁴;
k is used, as in Modern English, before e and i⁵, e.g king and kepte, and also at the end of a word, e.g. a__k (oak) and bak; however the spelling <ck> is rare at the end of a word; it is only required if the consonant is doubled, e.g. flock; note also that k is not used before n, as it is in ModE;
c is pronounced like ModE ch /tS`/ before [e e__ ae i i__], and at the end of a word, e.g. caep cest ci__ld ic aelc /tS`E`:p tS`est tS`i:ld itS` E`:ltS`/; elsewhere, c is pronounced /k/, e.g. clif cne__ corn /klif kne: korn/;
ch is also pronounced like ModE ch, but is only used before [a a__ o o__ u u__]; it is only needed for five words - chosen chusen;
in OE, <qu> and <z> only occurred rarely, in words borrowed from Latin, Greek or French; the same is true for eME;
similarly, in eME, <y> and <j>³ only occur in loan words;

Transform ModE spelling to eME spelling

Here are some simple rules which allow us to transform modE spelling to eME spelling and pronunciation:

oa/o*e > a__: broad, oak, boat, stone, home > bra__d, a__c, ba__t, sta__n, ha__m;
ee > e__: greet, deer, sleep, been, feet > gre__ten, de__r, sle__pen, be__n, fe__t;
i*e/y > i__: wide, wife, while, bite, fire, mine, by > wi__d, wi__f, hwi__l, bi__ten, fi__r, mi__n, bi__;
oo > o__: good, book, doom, flood, foot, goose, blood, moon, stool, tooth > go__d, bo__k, do__m, flo__d, fo__t, go__s, blo__d, mo__n, sto__l, to__t`;
ou/ow > u__: mouth, louse, house, now, cow > mu__t`, lu__s, hu__s, nu__, cu__;
ea > ae: deal, stream, read, beam, leap > dael, straem, raeden, baem, laepen;

Notes

this is true for most dialects of ModE, including southern England, North America and Australasia; however some of these sounds do still exist in the English of parts of Northern England, Scotland and Ireland;
note - eME short o should be pronounced the 'British' (or Australasian) way - /O`/; North Americans should either round their lips and cut their o short or look at the directions for eME long o__ and produce a shorter, sharper version of that; also note - Lass ¹ maintains that all eME short vowels were simply short versions of their long counterparts; in other words, that eME short e i o /e i o/ weren't identical to ModE short e i o /E` I` O`/;
j and v were simply variant forms of i and u respectively; they weren't separate entities in eME; their usage wasn't fixed until late in the ME period;
and in the middle of a word, after l and r;
in theory, k would be used before ae as well, but there are no examples at present;
which developed into yogh - y` in the early thirteenth century;

References

Lass, Roger. The Cambridge History of the English Language Volume II 1066-1479, Cambridge University Press, 1992; p50