Dutch Journal of Music Theory was created in 1996.
Journal of Music Theory was created in 1957.
Journal of Music Theory Pedagogy was created in 1987.
Music Analysis - journal - was created in 1982.
Leonardo Music Journal was created in 1968.
Journal of Research in Music Education was created in 1953.
Journal of the Society for American Music was created in 1983.
Journal of Music Teacher Education was created in 1991.
Music Theory Spectrum was created in 1979.
Society for Music Theory was created in 1977.
This was created around the same time music was invented. In order to play music at all, you must have good technique, posture...
Classical Music
I am not sure what music theory you are looking for. Music theory is very vast and required time and practice to know it completely. You can check out some music theory lessons at pianomother and from there you can learn the basic up to the advance lessons for music theory.