So in turn a musician may learn the language of music by ear, by wroterote, before being introduced to formal theory or only learn from imitation, hearing and repeating, and further by taking the learned information and building on this a self taught methodology.
The key question that myan adversary has pointed out so brutally that I have omitted is, "what does it mean to know music theory?" which is not even asked in the original question per se, but in an effort to save my butt here I will attempt to answer.
This training is taught in almost every western music school including universities and private institutions such as the Juilliard School of Music or the Eastman School of Music in addition to covering such things as modes, scales, harmony, melodic line, analysis, counterpoint (both tonal and species) but also challenges the student with intensive ear training, sight reading, private lessons on one or more instruments, composition, and playing in an ensemble. Pretty darn near covers it all.
Updated:
HowHow much does experience factor into a great performance vs. only theoretical knowledge?