Four versions, ranked in the order the Czar favors them. Your own order may vary.
Note-for-note perfect, a minimalist blend of spooky and sweet, Schuberts Ave Maria is one of those rare pieces that works whether it is played on a toy piano or by a full orchestra. Yes, this is Maria Callas bringing the pipes.
Bach did not realize he would be participating in a collaborative effort when he wrote his Prelude in C Major (BWV 846) but it turns out he did, when 137 years later Charles Gounod added a melody line to the words of the Ave Maria. The Czar likes Prelude and Ave Maria as separate pieces, but somehow the fact is was added on as a genuine part improvisation (Gounod did this on his own; his father actually and formally set the piece to the music) puts this one down at number two. (Even if it is the great Jackie Evancho doing what she does here.)
Mendelssohns Ave Maria is a longer piece intended to be more respectful, rich and lush. However, it winds up being typical of the Romantic Period in that it is a little overdone, and more like a Hollywood set piece than a real tribute to the Gregorian style.
Oddly, among the major versions, our least favorite is Mozarts. This is odd because normally Mozart hits it out of the park everytime. This piece by him seems to be a bit of an afterthought, as if he realized he needed one in his repetoire (K554). Still, a lot of people like it. One can see why.
And if you want a very different version of the Bach/Gounod piece entirely:
Dont be afraid to click on this last one. Very good, very funny, all at the same time.
Божію Поспѣшествующею Милостію Мы, Дима Грозный Императоръ и Самодержецъ Всероссiйскiй, цѣсарь Московскiй. The Czar was born in the steppes of Russia in 1267, and was cheated out of total control of all Russia upon the death of Boris Mikhailovich, who replaced Alexander Yaroslav Nevsky in 1263. However, in 1283, our Czar was passed over due to a clerical error and the rule of all Russia went to his second cousin Daniil (Даниил Александрович), whom Czar still resents. As a half-hearted apology, the Czar was awarded control over Muscovy, inconveniently located 5,000 miles away just outside Chicago. He now spends his time seething about this and writing about other stuff that bothers him.