how to download music for playing league

Having not the most optimal computer to play league with, having a youtube page open to play music while i play a game of league makes my fps drop down and ping rise slightly. I have found that if you use this free software to download the music on youtube it 1.) runs offline (so no fps drop) 2.) only downloads mp3 files (not too much memory required) and 3.) adds automatically to itunes (no need to fuss with it). Ive loved using it and hope you guys do too! Good luck on the Rift!