Found on Flickr user Tableauvivant’s page, this above photo shows the musical components of a Hallmark musical greeting card. I must say, this is quite surprising. I was sent a few musical cards back in May and when I took them apart, I found a tiny PCB with a piezo speaker and some other circuitry. This appears to be a speaker with gears and cardboard. Very cool. I wonder how you could hack this thing to make it play different tunes.