Best way to implement a "server" class in Java (Android)

I'm doing an application for Android. One of my classes is Sound which offers methods like playAlarm() and playSong(String name). Whats the best way to implement that kind of class,开发者_开发百科 as an object accessed with a singleton or as a static class with those static methods? From the point of view of app perfomance in Android.

There is probably little difference in performance but using a singleton instead of static methods will make it easier to unit test.

Barry