This question has plagued me for years, I have often wondered why all books sound the same in my head the first time I read them, then it hit me, the speech, the pattern of speech is always the same, it is always as I have typed above, and we don't always change the voice in our head if it says, 'gruff Scottish accent' just before or after, it doesn't seem to compute.
'Tis one theng to wroite loike that but it brengs a oddn' sound when ye readin' it in yer head moi lad if'n you'm were a finkin' o' typin' wif a h'accent.
This made the little voice in my head that read the speech change, I might use this in some of my future projects, but how to apply it? Of course one could use it in a third person environment during a dialogue, perhaps also when you begin to drift into first ready for a flashback, once in you could stop using it, or I don't know...

What do you guys think cos I'm stumped here...