What distinguishes a summing stack from a folder stack?

A summing stack is designed to combine multiple tracks together and enable mixing parameters for the summed output. This functionality allows for audio routing changes, meaning that the individual tracks within the stack can be routed to a common output, facilitating a cohesive mix. Additionally, a summing stack can apply processing, such as effects or EQ, to the summed signal, giving better control over the overall sound and allowing for adjustments that affect all included tracks simultaneously.

In contrast, a folder stack primarily serves organizational purposes; it helps in managing multiple tracks within the workspace without significantly altering audio routing or applying processing to the audio within those tracks. Therefore, the ability of a summing stack to modify routing and apply processing is what distinctly sets it apart from a folder stack.