If I understand Pat's answer he seems to be saying that composers of
the era were not consciously writing music that obeyed these
principles. So am I to take it that at no point was a composer
thinking "Ok, so this is the fundamental voice-leading note here, and
these other notes are not, and this fundamental note connects to this
fundamental note, so these parallels in between don't count."? That is
they were never thinking in terms of an underlying voice-leading
Pat's point was that they weren't thinking about the musical "grammar" of their music, much like you aren't consciously thinking about your English grammar - you have thoughts and you just type them out as you're thinking about them, and by and large your grammar will make sense. You can do this because you've (presumably) been speaking English your entire life - you've been steeped in it. So too were the composers of old. You also need to remember that they didn't have theory classes like you do. They studied with professional composers who put them through intense contrapuntal exercises.
Assuming this to be the case, and that they were not thinking in a
kind of reverse way to voice-leading reduction, the question then
becomes how were they thinking about voice-leading? We're they even
thinking about it at all? Just how much were they even thinking in
terms of voices? What for instance are we to make of some sweeping, 3
octave, rolling, left hand piano figuration? Is it really a collection
of voices with octave doublings and the like, or is it actually just a
harmonic cushion of sound?
Especially during the Baroque period, composers conceived of their music horizontally - a by-product of their contrapuntal development. The extent of vertical voice relationships then consisted primarily of consonances and dissonances; how / when / why to resolve the dissonances when they sprang up. Composers by and large did not think in terms of chord progressions as many musicians do today. The reason again being that their musical practice stemmed from their musical training. They were trained to think of music polyphony, so that's what they wrote, not homophony.
I think it is important for you to realize there is a distinct difference between parallel motion and doubling a part at the octave. I think it is also important for you to realize that you simply don't find sweeping, three octave piano figurations (apart from the fact that the piano wasn't invented until 1700) in Baroque and most Classic music. Romanticism would not wield its head until the early 1830's.
The ultimate question that leads from this is really how are we
supposed to think about voice-leading when composing? If composers of
the past were unconscious of their voice-leading practice does this
too mean that worrying about the intervallic relationships between
voices, or even what may or may not be considered a voice, is
something that should not really concern us?
300 years ago, the definition of music was very clear for Western Europeans. For young / new musicians such as yourself, it can be difficult to grapple with where current musical trends fit in on the historical timeline. I think it is important to realize that there is a difference between how music was written then versus how it is written now. Learning about historical practices does not mean that it was the "correct" way and that everything you learn now is in contradiction to it.
The primary difference here is that over the past centuries, composers have demonstrated what is possible. While I'm not saying that all possibilities have been exhausted, it appears that the focus has shifted from the model of: accept -> reject to what is it you're trying to say?
Invariably, you must be clearest with your intent. It is one thing if you ignore specific rules to convey your intent, it is another if you ignore them due to ignorance. Do not worry, musicians can tell the difference.
When I write music, I think about my intent, my goals. Do my voices need to be smooth or disjunct? Do I have voices or sound masses? Do I have individual textures? Music does not need to comprise voices. If intervallic relationships are important for your musical language, then yes, you should worry about them. If not, then don't.
Contemporary music is very situational. Because we musicians have proven what is possible, listeners generally accept the music at face value - their experience of the piece is contingent upon the rules (see, language and grammar) that you prescribe. Contemporary audiences don't listen with the same ears that you or I listen with. They will not slap their knee at how clever you are for starting a recapitulation in the parallel minor sub-dominant. They will not be upset if your [0,2,5,6] set is inverted the wrong way. They really don't care.
If you're going to write music, and I mean seriously write music, there are only two things you really need to think about:
- 1.) What am I trying to say?
- 2.) How am I trying to say it?
Once you answer those questions, the music writes itself.
Hope that helps.