The impact that wiped out the dinosaurs also wiped out all songbirds, except for in (ark) Australia. Australian songbirds then spread out to rest of the planet.
The closest living descendents (aka basal lineages) are the Lyrebird and the Rufus scrub bird. The lyrebird’s song is a mixture of its own song and other birds songs. They have been also been known to mimic chainsaws, car alarms, camera shutters, and human speech.
1: You’re talking about whether a common ancestor exists for all life, I’m talking about common ancestor for a trait (e.g. tree bark, bird song, these are traits and not organisms).
2: There’s current debate on whether life emerged multiple times or if it was only once. There’s evidence for both and it’s not a settled debate.