Oh boy, here we go. Where to start?
"I think the best definition I've heard, is music that is composed so that every note has a purpose, every single articulation, and every single voicing, etc. as opposed to just writing a melody and putting some block chords or arpeggios behind it with not much thought." [Please take more time proofreading your material. There were plenty of errors to correct in this single sentence.]
What you're describing is the modernist approach to composing, where no single musical element (pitches, durations, dynamics, etc.) is any more significant than another and should therefore not be ordered in a functional setting like we would in, say, the common practice period. Essentially, you're calling Free-tone (or Atonal) music "intellectual" when it's simply a different style. No more or less intellect goes into writing Free-tone music than goes into writing a Sonata. There's plenty of intellectual demand for both.
"E.G. a lot of twelve tone music is purely intellectual, it's built solely to satisfy the rules that Schoenberg established regarding that type of writing."
I find this statement grossly uninformed. 12t music is aesthetically pleasing to many people, including the composers who still use the methods of modernist writing in their works even today. I recommend listening to more music from the 20th Century.
"Perhaps you could call it
successful
intellectual music, I don't know. :P"
LAWL! As amusing as this is, I'd love to hear how we could possibly qualify music as "successful."
"I guess the most successful intellectual music is the music that doesn't forget what its purpose is: to be listened to, not just thought about."
Okay, so we aren't "thinking" about music when we "listen" to it? This is an honest, open-ended question... I'm curious what people believe about this, whether we're actually "thinking" about the music we listen to and to what extent.
"You can follow strict rules, but it still can be a simple piece... But I guess it is all in the terminology."
Yay, another semantic argument is brewing... though I definitely agree here that music can be written following a strict formula and still be simple. Actually, there are formulas for just about every style of music out there, including the "simple" kinds of pieces.
"Maybe you can compare the building of musical sentences with sentences in language. I've tried to analyze my musical sentences in terms of subject, predicate, verb etc. When I 'obey' these rules to the construction of musical sentences it seems to give a nice effect. It seems to be more 'correct'. Maybe you could say it sounds more intelligent.
I don't know if this is common knowledge. Either way I think this has to do with intelligence in music." [seriously, proofreading and spellchecker are great tools. Please use them.]
I don't think "structuring" music around language qualifies said music as "intellectual." Perhaps we rely on our intelligence when we compose music, but wouldn't that necessarily mean that every piece of music is "intellectual" since we rely on our intelligence to create music?