Artist’s description from DA:

Chandelier Swing was only the second foal born from Twilight’s experimental egg-splicing spell. After the success of the program’s firstborn (the Saffiplaid child Samosa Stripes), Twilight felt confident enough to tweak the spell at the request of mother Songbird Serenade, who hoped her daughter would not be born blind like herself.  Well, something went funny and, while the resulting earth pony baby was healthy—and full-sighted—in every other way, her lack of cries at birth quickly informed everypony that she was mute. Songbird (a deeply emotional mare when not doing her super-cool onstage thing), was at first devastated. Songbird regarded Chandi’s muteness as her fault, Twilight saw it as HER fault and Treehugger damn well saw it as nopony’s fault, as her kid AND her wife are perfect just the way they are.

Of course, life goes on and Treehugger is proven absolutely right. The family take joy in teaching their speechless daughter ways to communicate, especially with her sightless mother. Songbird and Chandi develop a unique finger-and-hoof tapping language that only they and Tree understand. To help the little earth pony communicate with the rest of the world at large, Tree teaches her sign language and, eventually, the family invest in wireless technology to give the kid a voice-processing smartwatch (in an Equestria that enjoys early 90s tech, this is pretty spiffy shit).

More applause is due for Gp3119, who helped me decide which direction to go with the Treesia scion.