This article shows you how to "loop" or repeat sessions within Hallow.
Begin a session. On that screen tap on the button in the bottom right-hand corner of the screen.
Tap on the circular arrows in the middle right-hand portion of the screen. The session will now play on loop until stopped.
If you click it once, it'll repeat all sessions in the queue continuously. Clicking it twice will limit the repetition to the first session only.