Function:
This is the metronome which changes sound and color every 8 bars.
At the beginning of every 8 bars, a triangle rings, and then the tick-tick beating of the metronome follows.
The number on the screen tells you which bar of 1-8 you are playing.
In addition to 8 bars mode, 2 bars, 4 bars and 6 bars mode are also available (to change the mode, tap the title).