Let's say you're using a source to activate scenes (or cues). Each time the source moves forward, it activates another scene. How can you make it go forward each 4 beats?
The super formula to put in the source's X slider is:
xtopercent(counter(0, grid.lastx, onbeat(trigger(music.1.low.beat, 0.07, 10, 15, 0.15), 4)))
Some explanations.
trigger(music.1.low.beat, 0.07, 10, 15, 0.15): this is the automatically generated formula when tracking beats on the low music frequencies. You can replace this by any input you want like a MIDI note or a OSC value, a DMX value...
onbeat(..., 4): this is where we specify a beat multiple, in this case 4. This means "pulse on each 4th beat".
counter(0, grid.lastx, ...): a counter that will go from 0 to the last cell index. It is incremented when the onbeat function pulses.
xtopercent(...): the counter returns the position from 0 to the last cell index, but since we're controlling the X slider, we need to return a percent value. So the xToPercent function just converts the x position to a percent value for us. It's a shortcut to avoid writing "counter(...) / grid.lastX * 100"
And in case you're wondering about the grid.lastX variable and why to use it instead of just putting the number (for example 10 if your grid has a width of 10), it's just to avoid needing to change anything when you resize your grid or want to use the same formula in multiple grids.
Cheers!