I've tried all music players for Android, but they all prevent my phones from deep sleep and thus consume unnecessarily too much battery. These include the Google and Samsung Music players that come with almost each and every Android smartphones and tablets.
The only one that does not do so called "wake lock" is Poweramp by Max MP. However, it has its own problem - using constantly about 1.4% CPU and causing an overall CPU usage to about 15% which is too high for just music playing:
After more searching and trying, I found another music player, MortPlayer Music by Mirko Schenk. It does not use any CPU at all, very nice (once again, German knows programming):
Like all other music players, it does wake lock though. Fortunately, there is a way to disable wake lock - Advanced Permission Manager by SteelWorks. Use this great tool, I successfully removed wake lock from MortPlayer and now I have a perfect player on my phone!
As you can see in above, MortPlayer is no longer in the list of wake lock offenders. By the way, Advanced Permission Manager can do much more, such as preventing many Chinese apps from auto start and crippling them. Another such great tool is Disable Service by wangqi060934. Many Chinese apps are very annoying, such as endless pop-ups, you need this great tool to disable their garbages.
Wake lock is a very bad thing to battery life. To check which apps do wake lock, use Wakelock Detector by UsumApps.
Constant CPU use is another very bad thing to battery life. OS Monitor by OS Monitor is the tool for this.
With above four mentioned great tools, your phone will love you, vice versa. And your music is now green , no longer blue.
Note: as long as music is playing, phone won't go into deep sleep. Even so, MortPlayer is still the best for the least CPU consumption.