As a matter of fact many of the medieval travellers when they met with ex-lands of bulgaria and macedonia laid weight on "there had exist only different slavic tongues instead of a common language"
These differences were still in place untill the beginning if the 20th century, when the mass education was introduced and the subjects started being taught in the modern literary Bulgarian.
You will fund these different dialects not only in the Rhodopes, but everywhere in Bulgaria. The Northern dialects are different from the Southern, which differ from the Eastern, which differ from the Shop etc, etc.
There is a very good reason for these differences.
For 500 years there was no centralized use of Bulgarian language.
There was no administrative use of it and the Church used Greek after the fall of the Bulgarian Kingdom under Ottoman rule. The low mobility of the people within the state brought to the localized development and use of the language. Every small community developed and spoke in its own vernacular.
If you come to the Rhodopes you will see that this is true even for two neighbouring villages only a few kilometers apart. The religious affiliation played no part here. People spoke the same dialect, no matter Christian or Muslim. Take for example Chepelare - it was a mixed village. Still people there spoke the same dialect. So you cannot claim that there is such a thing as "pomak" language.
I know that`s how you call it in Turkey, because the community that speaks in it consists only of pomaks.
But in Bulgaria all people, Christians and Muslims speak the same language within the given area.
And that is why we call all these vernaculars "selski govori - village dialects" as opposed to the more prevalent official language, which is generally used in big towns. We are still joking in BG that if you put two old men from Sofia and from Burgas in the same room, they will need a translator to understand each other. So this different way of speaking is valid for all Bulgaria, not only for the Rhodopes.
If you take a look at this, or for that matter if any Bulgarian looks at this, they will tell you they don`t understand it.
Yet this was the language of the land in the 11th-12th century. Since then the language has developed tremendously and today`s dialects and official language seem like light years apart from this old language. Yet if a trained linguist or philologist looks at it, they will easily show you the laws in which the dialects evolved from it.
The same happened in Greece. The old Greek was replaced with modern, because for 400-500 years of Ottoman rule, the spoken language got distanced form the old written Greek. Same happened in Bulgaria. That is why we have Old Bulgarian Language (Старобългарски език) and we have the New Bulgarian Language (Съвременен книжовен). Please do not mix the Old Bulgarian with the language of the Proto-Bulgars, as we still have no evidence how they spoke. The Old Bulgarian was the language that was developed here on the territory of the Balkan peninsula and which is a Slavic language.
