Though The 13 Voices all protect The Ageless Black, they're individuals and as such, have their own likes and dislikes and so have broken off into their own groups of friends (or "friends" as a particular duo puts it). These groups have become so concrete, that others have given them names. The Quartet is the "main group" since it consist of the "leader" Twist Tie.
Note 1: Voices are technically genderless, but for ease of communication, genders have been assigned to them. Use of they/them is also acceptable.
Not 2: Even though The Voices all come from the same source, they don't see each other as related to each other in a familial sense but simply pieces of a bigger whole, so while a Voice may be described as "sisterly" or like a "big brother," this is for descriptive purposes only.
Twist Tie is seen as the leader of The 13 Voices, probably because he's the most amicable of the group. He's naturally chipper and friendly, but also painfully blunt at times. Despite that, he rather use humor to defuse a situation than violence.
His Whisper is "Jump." When this word is whispered to the "Outside," deaths from accidental hangings and falls from tall places will occur.
All Voices have a Second Form used to fight Memories and other threats to The Ageless Black and the more humanoid it is, the more powerful it is. Twist Tie's form is nearly Perfect, making him the second most powerful of The Voices after Final Curtain. In this form, Twist Tie is still capable of complex thought and planning. He hasn't lost his sense of self and become an embodiment of his Whispers. Unfortunately, Twist Tie doesn't know the specifics of reaching a "calmer" Secondary Form, but he does remember having a strong desire to protect The Ageless Black in a particularly difficult fight against a Memory.
"Hm, was Final in trouble, too? I really can't remember. Sorry, buddy!"
Final Curtain naturally keeps to himself to the point of coming off as generally grumpy all the time. In reality, he balances out the other 12 Voices. As such, he's the most powerful of the group, to the point where he doesn't even bother to go into this (near?) Perfect Second Form most of the time.
His Whisper is "End," which causes cataclysmic damage to both worlds and it's even believed that if he were to Whisper while in his Second Form, he could bring an end to both worlds.
Oddly, Final cannot talk--at least in a way most can understand him. His voice sounds like metal pieces scraping against each other while being overlaid with static. Because he can't "talk" he technically can't Whisper, but he can snap his fingers to bring an End to things.
For some reason, Twist Tie can understand Final perfectly and when asked about what happened to Final, Twist Tie says he doesn't know exactly what happened, but he does know that Final didn't always sound like this.
Tightrope is the "Big Sister" of not only The Quartet, but all The Voices. She just has a protective aura about her and she especially goes out of her way to make sure the shyer Voices are looked after. On the other end of the spectrum however, she's quite reckless when it comes to her own safety.
Her Whisper is "Walk" which causes accidents that revolve around tripping or stumbling into busy traffic or stepping off the ledge of high places. Her Second Form isn't quite humanoid enough for her to have full control over it, so sometimes, she will be taken over by an urge to walk and will simply walk away from a fight for several miles before the trance breaks.
Afterglow is painfully shy, which could explain why she stays so close to Tightrope and Twist Tie, the only Voices she talks to on a regular basis. Being quiet isn't all bad though as this allows her to listen to more subtle voice changes and pinpoint exact emotions that others may miss in the middle of a conversation.
Her Whisper is "Sink" which causes accidental drownings. Her Second Form is just humanoid enough that she doesn't fall pray to her own Whisper.