This shows some sounds playing, as highlighted in green.
To continually loop a sound tick the corresponding 'Loop' checkbox before playing the sound. If the 'Loop' checkbox is left unticked the sound will play at random intervals by default and the number displayed as a label suffix is the number of seconds from the start of play before the sound is played again. To set the repeat period to a preset value then long-click on the button to display the screen shown below and enter the required value in seconds, which must be greater than or equal to twice the track time.
To cancel a preset value just long-click on the button again. To stop a sound just touch the button again. To adjust the volume of a sound once it has started playing just move the volume slider. If a Slave has been connected and 'Play on Slave' has been selected the button text is highlighted in blue when not playing.