Android > Multimedia > Audio
Volume Booster Plus

Try this speaker booster. It will increase your speakers volume up more than 20%
SnapMP3 - Music Downloader

Select a favorite artist, download their MP3-formatted music and play it on your mobile device
Beat maker - Super DJ music pads

Beat Maker - best DJ Mix pad & electro drum pad of super pads to make music
Youtube MP3 Download

Download and organize your favorite music from YouTube in MP3 format with this free app
YouTube Play Screen off

Gives users the ability to play YouTube videos in the background of their devices