Someone mentioned that if we went back in time, we'd have an idea of what is going on, but it wouldn't resemble the liturgy we have today. Do we have any manuscripts of earlier liturgies, from 1500, 1000 or 500 AD? I've always wondered how the modern liturgy evolved from older practices.
Apologies I didn't get to this earlier, I think I've said such things on this board previously.
Speaking strictly of Vespers, Orthros, and Divine Liturgy of the "Byzantine Rite", the current service books/typicon are not much changed from the 1300s are so. Prior to that, there were earlier forms of something similar to the current liturgy, and the further back we go the current books we use (Triodion, Horologion) disappear or change completely. The "original Byzantine Liturgy" was conducted in the churches of Constantinople, and is quite different from the current rites. A Greek cantor or priest (besides those who are also scholars of older forms) who was suddenly thrown into the liturgy would be completely lost because the order of services, church layout and chant were very different, though again their Greek should be good enough that they'd know what Psalms/parts of the liturgy are going on.
I believe some/all of the older books are in Patrologia Graeca, but further information can be had from:
Archimandrite Robert Taft, Liturgy of the Hours East and West (this is an excellent liturgy 101 level book. This is the only book of the three mentioned here that I'd recommend for the nonexpert)
Dr. Alexander Lingas, Sunday Matins in the Byzantine Cathedral Rite: Music and Liturgy (this one discusses in depth the music and some of the ritual of the old Constantinopolitan Orthros. For instance, ALL of Psalm 118 was *sung* with interpolated verses during Sunday Orthros, which itself probably took 45m-1h. Also, it discusses St Simeon of Thessolonica's complaints about "reform" in Byzantine chant of the time, which is still probably a "reform" or two before the currently accepted corpus of said chant. Though I found the PDF on the internet years ago, note that it's a disseration and is NOT an easy read for the nonexpert)
Archimandrite Robert Taft's books on the Liturgy of St. John Chrysostom ($2-300 and around 1000 pages of books, overwhelming for the nonexpert, but not otherwise a very hard read. Interestingly, elsewhere he uses textual analysis to "prove" as far as one can "prove" such a thing that St. John did indeed essentially write the anaphora of the current liturgy)