In general if two equivalent size engines have differences in cylinder numbers the sound will be from smaller cylinders, moving faster.

A 650 twin will have 2x 325 CC pistons firing in a specific order. Some with a 90 degree offset, others with 270. This just means “if one cylinder fires, where is the other one”. This can also have an effect on the sound since the combustion of gas in the cylinders is what causes the noise.

So there’s two larger cylinders firing in a different order.

In a higher cylinder configuration like a V4 or inline 4, the firing order is different, but also there are much smaller cylinders.
Generally a 600cc will have about 150cc cylinders, but firing much faster to get the same power.

It’s the difference of “big pops slower, or smaller pops much faster” and a little bit of what order the pops happen in.