Everyday in my day to day life, I have been observing people listening to music while at work. I wonder weather they really work ??? and if they are really dedicated to work , the next question is , are they really enjoying the music ??? I would say "NO" to both. Let me justify.
Here I compare our human brain to a computer processor. Even thought it seems like our personal computer is running different application at the same time, It actually schedules all the application processes in quick succession to make the user experience good. Likewise our human brain can only concentrate on only one voluntary action at a time. We can perform more than one action at a time provided the other actions are involuntary (Reflex actions).
For those who don't know about voluntary/reflex actions, let me cite a very simple example. You slapping some stranger is a voluntary action. And That stranger instantly slapping you in response is an example for involuntary or reflex action :-p
Now consider an example. Assume you are driving your car in a busy street for the first time with the music system on. I am sure that even though you have the music playing in your car, you can only hear it playing but you cannot actually listen to it as you will be busy concentrating on handling the busy traffic. Now driving is a voluntary action and you cannot enjoy music simultaneously which is another voluntary action. And as days goes on you will get used to driving in that same street and slowly it will turn into an involuntary action. Now you will slowly start enjoying the music as driving has became an reflex for you !!!. The worst case comes when you are listening to music while riding your bike. In this case you leave very little time for your brain to concentrate on driving and this leads to accidents most of the time.
It also depends on the nature of work to some extent. If your work requires too much of logical thinking(Software Engineers), it will remain as a voluntary action even if you get used to it and you cant even think about listening to music while working. On the other hand if your work hardly lets you to think, as days pass on you start to do it with your reflex and hence you are free to go a head and enjoy music as you can. So my conclusion is that people listening to music while working were either pretending to be working or just pretending as if they are listening to music. If you used to listen music while working, just think in which category you fall.
Think !!! Decide !!! Think different !!!