I never said music is anything like a "language," because it really isn't. We use a lot of the same brain functions on both, but one thing isn't the other as there is still a substantial difference.
You can't be "as clear as possible" with a message in music UNLESS you start employing symbols that culturally mean something and/or using other things like text itself (Eg Operas, or a symphonic poem based on a literary work.) Music itself, by itself, is extremely poor at communicating anything without aid of cultural symbols since those are the ones that we actually recognize as "meaning" anything.
Likewise with a language you don't understand, symbols that you aren't familiar with aren't going to "mean" anything to you by themselves (which isn't to say you can't get emotional meaning out of them as I said in my previous post.)
Example 1: Baroque affects worked within a cultural context that understood that if a piece was in X key, it MUST represent Y emotion with Z techniques. Hearing baroque music now without this knowledge doesn't mean you can't enjoy it all the same, but the meaning of the techniques, keys, etc are going to be lost on you. A piece in D minor isn't just a piece written in "minor" and it could be any key, as it happens later on in music history.
Example 2: Hearing medieval music and the constant parallel 5ths, etc, wouldn't lead to anyone this day and age to think "Oh, it's a perfect 5th interval it represents the perfection of god!" without being told beforehand about this aesthetic reasoning, since our music sounds -vastly- different and a lot of church music people are familiar with is much newer than this.
In both cases the composers may have thought they were "as clear as possible," but stripping away cultural context can lead to entirely different interpretations of the music which itself hasn't changed. I would say that, right now knowing how language and music are related it'd be easier to write music specifically designed to be interpreted universally (in the majority of cases) as having X or Y emotion, but the best you can get out of that is a general direction. Emotion isn't just "sad" or "happy," after all, and for everything more nuanced than the basic emotions people tend to fill in the blanks with their own experience and cultural context, adding layers to a basic idea without the music needing to be changed or be more complex or anything.
Example: Opera. A death scene and a departure scene may share similar sounding music, if not the exact same music, but the context of the scene can change wildly what the music provokes emotionally (specially after seeing the scene and hearing just the music.) Likewise, if the music IS different, it's probable that the base characteristics of "sadness" are going to be there still and that anything on top of that is due to the scene itself (such as dramatic pauses, etc etc.)