You said that you want to make a language that "sounds Celtic". What do you know so far about the Celtic languages?
At least some of them use vowel mutation for plurals. There tends to be a fair amount of silent letters (at least in Irish, Scottish and Manx, the Q-Celtic ones I think) and pronunciations that are somewhat complicated and hard for me to figure out.
I'll grant you that the orthography can be challenging for novices, but Irish really doesn't have much in the way of silent letters; since the spelling reform of World War II, the script has been practically phonetic. Scottish Gaelic still uses the traditional orthography which, like the spelling of English, was fixed centuries ago.
That last one especially applies to Manx, I think.
Actually, I think it applies less to Manx, since its orthography only began to develop in the 16th century. Classical Irish (the ancestor of both Modern Irish and Scottish Gaelic) already had a written tradition stretching back over a millennium at that point.
An example of unexpected or difficult (my value judgement) lettering is the w vowel or the ll in Welsh or the vowel strings (aoi, oi, ea, etc.) in Irish.
as both a vowel and consonant never struck me as confusing in the least since it's exactly what we already do with y
. The earlier spelling for ll
, which might be more intuitive for English-speakers. But again, Spanish got me used to the idea of ll
having an unusual value.
The reason you are confused by Irish digraphs is that you don't understand that they have two functions, only one of which is to show the quality of the vowel. The other is to show the quality of the consonants
flanking it. Irish has phonemic palatalisation
. This means that every consonant has two distinctive versions, palatalised and unpalatalised (generally velarised). Russian is the same way, but it solves the problem by having two characters for every vowel and using "hard" and "soft" signs.
So the reason for a spelling like ea
is that it shows that the vowel is /a/ while the consonant before is palatalised and the consonant after isn't. Thus, cead
"permission" is pronounced [ˈcad̪ˠ]. Without the e
there, you have cad
[ˈkɑd̪ˠ] "what". And if the second consonant is palatalised (or "slender", in Irish terminology) and the first is broad, you get caid
[ˈcɑdʲ] "football". (Using Russian orthography, these three words would be кяд, кад, and кядь, respectively.)
This is part of why I think your conlanging efforts here are fundamentally misguided. You're mimicking the spelling
of Irish without an understanding of how the characters are being used or what they represent. The pronunciation of Aoireas
if it were an Irish word (it isn't, but we do have aoire
"shepherd") would have to be ['iːɾʲəs̪ˠ].