This was posted by laszlo:
"Until the XIX Ecumenical council (Trent) the Liturgy was not centrally coordinated. The basic principle: Lex credendi => Lex orandi was was observed, the Liturgy followed the principles of Catholic faith, but the same doctrine can be expressed by different ways.
Practically every diocese or religious order could have her own Liturgy, and many of them actually had. This had a very easy reason: the Liturgy (adding new celebrations of forms) was constantly changing and before the invention of the printing of the books it was impossible to provide the whole Church with standardized copies.
The differences were not only in words, but also structural. The Roman Canon consist of separate prayers and with insignificant variation is the same throughout the year, the Eastern Canons (and the Mosarabic in the Western word) are continuous prayers and there are different canons for different occasions.
The Gallican Liturgy started in the turn of the second millennium, an mushroomed in the 15th and 16th Century. It was characterized by the abundance of hymns (sequences) and processes, from which the Entrance, Offering and Communion process was reinstated in the 1970 Mass. The printed books exaggerated the variations everyone pushed his own liturgy.
St Pius V ordered the Central command over the Liturgy, ordering the renewed for of the Roman Liturgy all over the world. Only a few religious order and the Toloose (Mosarabic) and Milan (Ambrosian ) dioceses get exception. (In England the Catolics were illegal in that time, the Sharum or any other remainder from the Celtic rite did not get legality). As a matter of fact both the Mosarabic and Ambrosian rites were abandoned during the following Century for the favor of the Roman rite and revived only with the liturgical reform of the 20th Century.
At this moment outside of the various Eastern Catholic rites only the Ambrosian and Mosarabic rites are accepted, and as far as I know each underwent some changes, the Eastern Catholic rites even toward the vernacular during the Liturgical reform of the 20th Century.
I made a compendium of the Western rites
it is a dynamic page, select the rite and language at the top for comparison. 'Source' link at the bottom list the sources of the versions. It is not scientific (the textual critic need serious lifetime research) but gives some overview. It would be worthwhile to include the more diverse Eastern Catholic rites too."
I found this fasinating at the website he created here: