Jigglypuff
Chat with our AI personalities
a chatot can learn sing
rhypirior loves protector
Magmar
When looking at the item, it does say "a Pokemon loves this item". It is a hint to give a Pokemon that item. Well that Pokemon is a rhydon. Give a rhydon that item to hold. Trade it and see what happens...
Sing isn't a TM in the game. Some Pokemon can learn it naturally through level up, though.