*Playing by ear*
I hear a song and I go, “I wonder if I could play that?” and I mess around for a few minutes until I’m like, “Ok, GOT IT!”
Some are tricky for no particular reason. The chord progression for “Radioactive” from Imagine Dragons stumped me for a few minutes, as did the chord progression from one of the Minecraft songs a few years back.
But once it “clicks in” – it’s like unlocking a door and stepping through.