Sister musician horses, basically.

Legato is a character that's been around for much longer (since 2014) and I revamped her design in 2018 to derive away from her original purpose of being a My Little Pony: Friendship is Magic OC. Burletta was made at the beginning of this year (2018) and was solely made under the same motif design Legato was under.

Other than that, no further correlation shall be made between 'MLP: FiM' and these characters.