Since singing in audios is such a controversial topic right now, I'd like to add my opinion because sometimes I hate it and other times I don't. The times I hate it are when it feels deeply unnatural and halts any progression of the plot. This usually happens in situations where absolutely no one would actually be singing, and it's usually forced into so VAs who are proud of their singing abilities can show off.
There are good examples though! I really really love it when VAs sing in a way that feels natural and fits with the plot. One of my all time favorite audios is called "Dude, Give Her Your Jacket!" from SoulBrotherAudio. There's an amazing scene where all the characters sing along to the radio in their car and it felt alive and realistic. It was so endearing and didn't make me groan like the audios where they stop the plot in its tracks to sing for no reason. Another one I really like is the siren's song in Blue Infinity. It's a more plot based series, you know the song from a music box, and when you finally hear the siren sing it for real it's a huge reveal.
Sorry if this was too long. I actually like singing in audios as long as it feels natural and doesn't break the pace of the plot.