How do I quit doubleTwist Music Player?

The Android operating system will dynamically allocate resources based what your device is doing. There is no need for a "quit" function or to "close" the app because of this. When doubleTwist Music Player is in the background, it will sleep and consume very little resources.

Google has published their stance on this on their developer site.

"By default, every application runs in its own Linux process. Android starts the process when any of the application's components need to be executed, then shuts down the process when it's no longer needed or when the system must recover memory for other applications."