answer:As I understand it, it’s similar to how scientists date trees based on their ring structure. If you look at a tree’s rings, you will see a pattern of big rings and small rings. A tree grows a ring each year, so the size of the rings corresponds to how well the growing season went in a particular year. So, let’s say you find a tree with the following pattern of rings: B-S-S-S-B-S-B-S-B-B If you find that same pattern of rings in another tree, chances are both sets of rings were formed in the same stretch of 10 years. In fact, if you find any tree in the area with that pattern of rings (BSSSBSBSBB), you can be pretty sure that those rings all grew in the same ten-year period. Thus you can date trees in an area relative to each other. Now think about a song’s melody. At any given point in a song, the melody either goes up, or it goes down. Right? You don’t need to know the exact notes, or the rhythm, or the words or instruments or anything. You can create a pattern of any song simply by listing a pattern of “ups” and “downs” for its melody. And just like tree rings signifying the same stretch of years, these patterns turn out to be pretty unique indicator of a song. U-D-U-U-D-U-D-D-D-D-U-D is probably a unique pattern for a unique song. I’m not 100% sure this is how it works but I’m fairly sure.