Clicking on the 'Metronome' button at the bottom of the page will open the Metronome settings pop-up page (only available for OpenSong songs, not PDF files, etc). If you have already set the metronome values for a song, long pressing the metronome button will stop/start it.
This is a feature requested by loads of drummers (and others who need to keep strict timing during a performance). The metronome is a 'click/beep track' that follows a specific tempo and time signature, emphasising the first beat of each bar.
You need to ensure the song has a time signature and tempo (40-199 bpm) saved to it for the metronome to work. You can start the metronome by clicking on start. The metronome will restart when you move to another song (assuming it has a time signature and tempo set). If you'd rather see a visual metronome cue, turn the volume to 0% and switch on the Visual metronome. This causes the top title bar to flash in time with the metronome. Each beat triggers an on/off flash.
I have included the most common time signatures (2/4, 3/4, 4/4, 5/8, 6/8, 7/8) and allowed tempos between 40 and 199 bpm, but if you feel this needs more options, please email me - I'll add it (within reason!).
You can also tap the tempo button to easily set a tempo. This method averages your taps to give you a steady beat. Pausing more than 2 seconds between taps will reset this tempo and let you start again.