Minor edit from me adjusting the cropping. The original SVG file was not sized to the actual art.
Published: Feb 21, 2015

"Hello? We sing like all the time. It's how we get people to do what we want."
Of the three Sirens, I personally think Sonata is the cutest and most likeable. She seems the most likely to walk away from everything and live as a normal girl… and maybe even develop a singing talent without magic. (Not to mention that her "It's Taco Tuesday!" line was absolutely adorable.) Furthermore, it looks like Sonata is left-handed. Notice that she holds / does everything with the opposite hand to Adagio and Aria.
I had a unicorn and pegasus already, so Sonata is an earth pony by default. Her cutie mark is a music note on a heart, which is featured on her shirt and later, her dress. Given that a cutie mark is supposed to reflect their talent, Sonata must really love singing.

Additional Files: Cutie mark
Vector all the ponies: gallery | journal | SVG files
Reuse: — No bases — No use for commercial (profit-making) purposes — Include a link back here

Edit to an image vectored from episode 2x15: The Super Speedy Cider Squeezy 6000. The Sonata Dusk character and My Little Pony: Friendship is Magic are the property of Lauren Faust and/or Hasbro and/or others.