Answer by Josh Siegle, Ph.D. student at MIT:
Think about music as a sandwich.
Like a sandwich, all music has three components: the lows, the mids, and the highs. These correspond to the meat, the bread, and the toppings, respectively (vegetarians can substitute tasty portobello mushrooms or falafel for the meat).
We all agree that without the bread, it's not really a sandwich. But without the meat and toppings, it's not really worth eating. Similarly, the mid-range frequencies carry the main content of the music—the vocals, the soloist, or the melody. You can listen to the mids alone and still tell it's music. But without the low-end (the meat), it's not particularly satisfying. And without the high-end percussion and harmonics (the toppings), it's not particularly interesting.
The musician's role is to design the sandwich. They make a bunch of experimental sandwiches on their own until they find one that's both delicious and original. If they think others will enjoy it as well, they record it for posterity by writing down the recipe. When you get your hands on a record, CD, or MP3, the recipe is all you get. There's not actually a sandwich there, just the instructions for creating one. So how are you going to make your sandwich?
The easiest way is to go to 7/11 and buy a pre-made sandwich for a few bucks. It looks like a sandwich and tastes like a sandwich, but the quality is poor, and it's probably missing many of the details the artist intended. Is that really a leaf of fresh watercress, or is it a wilty, week-old piece of iceberg? This is analogous to using the earbuds that come free with your iPod. What you're hearing is a poor reproduction of the original. It may be satisfying for some, but once you know what you're missing, it's almost unbearable.
At the other end of the spectrum are the gourmet sandwich shops. They aren't particularly wallet-friendly, but you get what you pay for. These places have the wherewithal and the patience to recreate your sandwich exactly as the artist envisioned it. If the recipe calls for pork loin smoked for five days over hickory wood, that's what you're going to get. If the bread is supposed to have poppy seeds, they will be there in abundance. The ingredients will be fresh and the flavors will be rich, so the steep price is usually justified. Obviously, this is similar to using high-end headphones. If you're not accustomed to listening to such detailed music, you might not realize there's a difference. But once you've gotten used to it, the disparity between a nice pair of Sennheisers and those white earbuds is like night and day.
When listening to music, you don't just have to make sure all the ingredients are present, but also that they are balanced. Too much high-end is like a sandwich slathered in sauce. It may be palatable, but you won't be able to pay attention to anything else. Loads of low-end is like a sandwich stuffed with several inches of meat. It might be enjoyable once in a while (and fun to brag to your friends about) but you don't want to be consuming it at every meal. And it definitely doesn't work well for every style.
The next time you wonder why musicians are so fussy about how people listen to their music (128 kbps through laptop speakers? sheesh.), or why audiophiles go to great lengths to find headphones with perfect spectral characteristics, turn your thoughts to sandwiches. Just as you can taste the difference between a well-made sandwich and a crappy one, many people can hear the difference between finely crafted headphones and their $10 counterparts. Headphone selection is (hopefully) not about being ostentatious, but about finding a tool that can keep your music collection fresh and tasty for years to come.
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