In all of these ‘gn’ words the ‘g’ is silent—not pronounced. They all came into English from French fairly early and have been thoroughly ‘naturalized’.
Words with ‘gn’ which came into English directly from Latin, such pugnacious, preserve the /g/ sound. But some of these have French-mediated cognates without the /g/—impugn is one such. Signature, although it came into English from French in the 14th century, was at some point reinterpreted as if it came directly from Latin signatus, and is pronounced with the /g/. Your magnolia is even more curious—it derives from the name of the French botanist Magnol, but by way of the Latinized botanical name of the plant (which was conferred upon it by an English admirer), so it pronounces the /g/.
There are some ‘gn’ words from Greek; these preserve the /g/ when it follows a vowel (agnostic, anagnorosis), but not at the beginning of a word (gnostic, gnome).
There are many more recent words from both French and Italian which are so to speak ‘permanently resident aliens’; these retain their native pronunciations (more or less—you might not be very happy with our pronunciation of terms from your own language) with /nj/: cognac, lasagne, carmagnole, bagnio and gnocchi.
Finally there are the words starting with ‘gn’ which descended from Old English. These all retained the /g/ into Middle English down to the period when spelling began to be regularized, but subsequently lost it. ‘gn’ inside OE words lost the /g/ sound much earlier, which is why the letter ‘g’ no longer appears in (for example) rain < OE regn.
ADDED:
And Jim reminds us of gnu. Dictionaries license both /nu:/ and /nju:/; the word is variously said to derive via Dutch gnoe from Khoikoi gnou or Khoikhoi i-ngu repesenting Southern Bushman !nu:.
I am not a native speaker, but I think I can help a bit.
You are right: 'the American pronunciation of "accept" is awfully close to "except"'. This is quite true because the sound of unstressed syllables in English will generally shift toward the center vowel, the schwa (ə).
But if you look up a dictionary, many of unstressed syllables will still be transcribed distinctively, because if you listen carefully you can still hear the difference between that vowel and the schwa sound. (Also note that they will get even closer to the schwa if the entire word is unstressed.)
According to my Free Dictionary app (AmE), accept is pronounced [ak-sept], and except is pronounced [ik-sept]. Another app (BrE) transcribed accept as either [ik'sept] or [ak'sept], and except as either [ek'sept] or [ik'sept].
- Your first sound clip (accept.mp3) is [ak-sept], and the other one (ukac___020.mp3) seems to sound like a schwa ([ək-sept]).
Both dictionaries transcribe the unstressed syllable of accord similarly (though with different symbols): [uh-kawrd] in AmE, and [u'kord] in BrE. (This [uh] or [u] sound is similar to the sounds of the first syllable of ado and about.)
One thing to keep in mind about English pronunciation is that it could vary very widely among English accents, especially the vowels. This IPA chart of English dialects might provide a little too much information, but it captures the differences among various English dialects quite well.
Hope this helps.
Best Answer
Is there a reason?
Yes, there is.
First of all, there are no rules that tell you how to pronounce an English word, based on its spelling.
Let me repeat that:
That may be a bit shocking, but it's true.
But, but, there must be rules, how else do people know how to pronounce words?
Well, it's a common mistake to think that we pronounce words as they are written; it's the other way around: we write words as they are pronounced.
Now, in the case of English, spelling was decided on quite a long time ago for most words. The difficult part is that we spell English today in a way that it was pronounced a long time ago.
That's the short version. There have been some spelling reforms (for instance, Noah Webster did his best to make American English spelling more "logical"), but the main idea is just that: we write English the way it was pronounced a long time ago.
This means there are many words that are not pronounced in the way you would expect when looking at their spelling. One of the best illustrations of that is the poem The Chaos. It was written by Dr. Gerard Nolst Trenité, a Dutchman who probably felt the same frustration as many learners of English when trying to figure out the relationship between spelling and pronunciation in English.
There are different things that influence spelling, this answer is hardly complete. For a more detailed post on that, please see this excellent answer by Ben Kovitz.