mercury aspects + the sound of voices
The conjunction is the only aspect possible between Sun and Mercury, so if someone has this aspect, it is likely that their voice is full of confidence, there can be a rich quality to their voice, they may speak with plenty of precision and are not ones to stumble or stammer; they come across as though they know a lot of information.
Mercury-Moon aspects could indicate that the person has a really soothing voice, full of calmness and serenity, speaking softly and femininely. They may have a type of voice that you feel like you can trust and confide in, because they are so gentle through the way they communicate.
Mercury-Venus aspects could indicate that the person has a beautiful voice, a voice that is highly appealing and sweet. They may also be talented at singing because of their lovely voice. They sound very melodic and charming.
Mercury-Mars aspects could indicate that the person has a striking voice, their tone of voice may be brash and probably sounds harsh. They might often sound angry even if they are not actually angry. These natives are also known to speak with tons of passion and intensity, and aggression.
Mercury-Jupiter aspects could indicate that the person has a pretty loud voice, and they make sure that their words are being heard, so therefore their tone of voice is prominent. People with these aspects are prone to laughing a lot, and often have long, loud laughs, which gives them an endearing quality.
Mercury-Saturn aspects could indicate that the person has a quiet, reserved, and respectful tone of voice. When they speak, they seem composed and could have a wise way of speaking. Their voice is often monotone and they usually talk dryly, at a relatively slow pace.
Mercury-Uranus aspects could indicate that the person has a unique voice; maybe their voice is quite different, or stands out among the rest. Think of Morgan Freeman: one of the main things he is recognized for is his renowned voice (he has Mercury conjunct Uranus). These natives attract interest through the way they speak because the voice is typically dissimilar from most.
Mercury-Neptune aspects could indicate that the person has a dreamy, poetic, sleepy tone of voice. They sound laid back and nonchalant, but also with an enchanting quality to the way they speak. Their voice is chilled out and mellow, and they may sound a little shy.
Mercury-Pluto aspects could indicate that the person has a powerful, dominant, and heavy/deep tone of voice. Lauren Bacall had Mercury sextile Pluto and was admired for her deep voice, which sometimes intimidated and intrigued others at the same time.