I use this little contraption both at home and work to play all the music I want, and it keeps my phone free to make and receive calls.
I found it annoying that the Samsung S4 doesn't automatically mute incoming messages and notifications when I'm jamming to music through the earbuds. Since I get a lot of notifications, the music cuts out just so that the phone can ding at me. Hate that. Also when calls come in, the music again mutes and pauses.
You just can't rock it out when the music keeps cuttin' out like that, so I found another solution.