Can You Hear Me, Major Tom?

At work, I listen to music via headphones extensively. It’s interesting what you hear over headphones that you don’t tend to hear while listening on a home stereo or in your car. Even songs you know intimately can sound significantly different. Today I was listening to the song "The Modern Things" by Bjork. I would guess that I’ve heard this song at least fifty times, and that’s a conservative estimate--I remember Post being a staple of my CD player for the better part of two years. But while listening to it today, I noticed that she sampled a panning xylophone bit from Esquivel (the early 60s stereophonic pioneer and godfather of space age bachelor pad music). And it’s not like it only appears once, it’s throughout the whole song. How had I missed this for so long? Either my ears are that inattentive, or it’s the difference of the headphones. I’d like to think the latter, else my job as an acoustics engineer may be in jeopardy.