About 10 years ago my wife and I got two recues. A female greyhound and a male lurcher (who basically looked like a greyhound). My wife used to try to get our dogs to howl, because she thought it was funny. It turned into something they would do on command. Anyway, about 8 years ago my wife discovered the song "Werewolves of London" by Warren Zevon. At the appropriate parts of the song, she would command our dogs to "sing", and they'd both howl. Yes, hilarious. Anyway, about 7 years ago the greyhound got osteosarcoma, a painful bone cancer, and we had to put her to sleep. The lurcher was extremely lonely, so we rescued another greyhound. My wife didn't put the Werewolves song on again, because it made her feel sad. Fast forward about a year, and we're both in the house doing whatever, and I put on a playlist, not realising the song was in it. As soon as the first bar of the song played, the lurcher jumped up onto the armchair at our front window, frantically looking into the park out front, howled, and ran around the house "searching", presumably for Pasha. Tears, obviously. But also the realisation that a dog can recognise a song, years after last hearing it, in a sea of thousands of other songs. And within the first few seconds of it playing. Honestly, I was astonished.