Yes! They were political, but their audience was much more limited that Christian rock or even a modern day sermon would be. IIRC Ildar Garipzanov covers this in his book The Symbolic Language of Authority in the Carolingian World (c. 751–877). For the Carolingians at least, psalms, praryerbooks, etc. did have political undertones. Sometimes the prayer would have a special tailored message for the silent prayer that would only be read, thereby limiting the audience to those who were literate and allowed to read the prayer. Garipzanov seems to argue that the message generally relates to representations of the king vis a vis the church, and whether they should pray for the king, the king and his family, etc. It is a pretty interesting chapter and his book overall is really good, I would recommend reading it if you can get a copy. He covers other things such as coinage, seals, letters, and titles.