Posted this a long time ago, figured I'd share it again since it was fun to share with some added points.
So, Sona's voiceover, like a lot of old champions, is pretty basic, and outdated since she refers to her Summoner a lot, still.
Obviously these types of things can't be rectified so easily because of availability of Voice Actors, but what other players in the game hear is her emotes, which are all musical cues. So, I present an idea:
What if Sona was given special taunt and encounter interactions with other champions, both allied or enemies, where she plays a brief snippet of that champions login theme, or other piece the champion is associated with. Obviously not an exact soundalike, but in a style similar to how Silent Night Sona plays little snippets of "Deck the Halls".
Example: When taunting or first encountering Kindred Sona could play either a little snippet of their login theme, or the small tune that Lamb sometimes hums.
Heck, imagine loading into a game as Camille jungle, and you head to your buff and your allied Sona follows behind you, and you hear a brief, very-simplified string version of the violins of Camille's login theme. I think that could definitely be a really cool little thing to encounter at the start of the game!
There are plenty of champions with great, recognizable scores, like Camille, Xayah & Rakan, Pyke, Jhin, Taliyah, Ekko, Kled, etc and I think it would be a perfect way to add a little flavor to Sona as a world-class musician, and it would require no actual voiceover work!