While I imagine Google probably does handle transpositions, people do tend to remember the pitch of a song, even if they don't have perfect pitch: https://en.wikipedia.org/wiki/Absolute_pitch#Pitch_memory_re...

> While very few people have the ability to name a pitch with no external reference, pitch memory can be activated by repeated exposure. People who are not skilled singers will often sing popular songs in the correct key, and can usually recognize when TV themes have been shifted into the wrong key.