I think the time signature meter example on the home page of pyramid is wrong
It shows 4/4 ( green ) that is 4 quarter notes in a bar against 3/4 ( yellow ) which are 3 quarters notes in bar .
Which means they both have exactly the same beat duration = a quarter note .
BUt the 4/4 meter last 4 beats , where the 3/4 meter last only 3 beats
This is an example of polymeter , when 3/4 (yellow) reaches it’s last beat it should restart , at the point where 4/4 (green ) reaches it’s Fourth beat .
Polymeter : de-synchronizes themselve ( different number of beats )
Polyrytm : diifferent beat value play within the same bar
The example shown is faulty because it shows they both end their bar at the same time , which is wrong .
3/4 ends faster
4/4 = 1-2-3-4-1-2-3-4-1-2-3-4-1-2-3-4-1-2 =green
3/4= 1-2-3-1-2-3-1-2-3-1-2-3-1-2-3-1-2-3 =yellow