I am running 10.11.2 captain on my mac book pro
Reseting the system management controller SMC should have resolved the problem as per advice from on line chat with apple iTunes support; however the problem has not gone away as I did play remote to my Mirantaz Receiver to Bose speakers; the airplay drops still intermittent. To understand if it was related to the operating system upgrade of apple I used window 7 lap top and it appears to play fine.
Conclude: Apple 10.11.2 and earlier version seems to root cause; apple must fix this issue as I play apple music via subscription of $12/month.
I suggest you try this trouble shoot and let me know if your work.
steps
Before SMC reset press command option escape to force quit any application and put to sleep mode; wake it up and do a restart and do a shut down.
Mac book with non removable battery reset method
Plug magsafe to power source.
on built in key board press all the buttons at same time Shift-Control-Option and RELEASE AT THE SAME TIME.
PRESS POWER BUTTON to turn on computer.
CHECK THIS METHOD as it a document link sent sent to me from apple support.