To help with the contest, feel free to add your own suggestions below and I may add them in an update;

-Octavia Melody is a grey earth pony/girl with Long and straight Black hair in equestria who plays the cello, and has appeared in the show as a background pony, but has had speaking lines. Is often in a lot of stories with Vinyl, Lyra, and/or Bon Bon
-Sonata Dusk is a blue siren/girl with a blue pony tail in equestria.
-the siren. She was one of the three main villains in rainbow rocks along with Adagio and Aria. The sirens have magic that causes disharmony through their singing. When the rain booms defeated them, they were without magic and couldn’t sing, but edventualy re-learned how to sing normally
-Sonata likes tacos, but, at least in most of my Sonatavia stories so far; Octavia likes salads. They often compromise on taco salads ^^
-they’re both into music
-Much like another, more popular, Octavia ship. One where the other person is also silly and somewhat an opposite to Octavia. So what’s the difference/Sonata be a better choice? Well, depending on your headcannon, Sonata’s actually 100’s if not 1000’s of years older! So she kind of has the Sunset Shimmer effect; still a child, but actually rather mature despite the age she looks. An excellent compliment to Octavia more common interpreted personality because of her upbringing. Speaking of;
-both come from toxic family relationships (although in some cases, Aria/Adagio can sometimes be ex’s)
Octavia family with its upper crust mindset and desire to mold her into perfection as seen in most interpretations. While Sonata, at the best of times, is always treated like a joke to the other dazzlings. So both have something to feel empathetic about, and that need to/can work through together
-Sonata’s a villain. Easy to forget, but she did try to take over the world. How does this fit well into Octavia? Well Octavia was one of the people she mind controlled. So, I’m them forming a relationship, it be something she’d feel guilty about. Perhaps at first just seeing Octavia as someone she can help make right. More true so, arguably, because of the showcase being turned into a battle of the bands instead, Octavia got humiliated and defeated in the first rounds.
-Writing around the more popular ships;
Vinyl- I find the best way is to either have been straight, Octavia likes her, but it’s tragically one sided. Or, ship with someone else. Often I’ve gone with Pinkiescrath. Honestly, the only reason this is so common cannon in SonTavia at the moment is, one, to give Vinyl someone since Octavia is taken. Although why Pinkie? Well, just prior to discovering the joys of SonTavia, I discovered the wonders of Piñata (pinkie sonata) in pinkie pie swears. So kind of was more addressing that and how that ship actually makes a little more sense.
As for Sonata, I usually see her shipped most with Aria and Adagio. If their sisters, that solves any problems. However, if they’re ex’s, I find it more effective for Sonatavia when Sonata was in a more toxic relationship with either prior. Which isn’t that much of a stretch considering Arias personality and how they think she’s a joke in cannon
-I’ll just say this now; I hate the idiotic bubbly depictions of Sonata, and Pinkie while I’m at it.
I get it, they can be both silly, but being optimistic, dosnt mean you have to write someone as such to just be stupid. You can, and should, also try to write them with some dignity and sense as well.
The smile song is loved because of that moment that addresses there are sad days, don’t be afraid to add those

-they’re both hot. THERE! I said it >.> but while this is the most opinionated, there’s just something about the duo that the most attractive to me, and a lot of people based on the Derpburioo numbers.
-sonata makes Octavia laugh, Octavia pushes sonata to be taken more seriously. Kind of already adressed that, just clarifying.
-lastly, they look cute together.

That is all :3 Now get out there, and write/draw your own SonTavia works!!

See every story written so far here!

Art by The Sleepless Beholder,
Love those guys!

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Some ideas for stories I may do. I claim no monopoly on them, so if you’re struggling for an idea for the contest, feel free to use, and possibly check back later for more ideas:

-Octavia and Sonata go to see a musical/concert together
-Octavia comforts/helps Sonata deal with the loss of her magic/mortality. Or with enough AU power; Sonata outliving Octavia
-A story where The Dazzlings defeat the Rainbooms, until a certain grey student catches Sonata’s eyes ❤️
-Sonata/Octavia meeting each other’s families for the first time
-Octavia/Sonata talking the other to break their toxic relationships with Aria/Vinyl
-Something simular to Pinkie Pie Swears, But sonata meeting Octavia before the battle of the bands
-Octavia and Sonata picking out a pet to adopt at the animal shelter
-Sonata trying to get Octavia a gift
-Sonata and Octavia go to equestria, and Octavia sees sonatas true form!
Sonata as a mermaid who saves Octavia’s life