In the sig~ help file, the sig~ object is used to feed a cycle~ object with a constant signal. Why is the constant feeding necessary? Why not use the flonum directly?

difference-between-sig-cycle-and-flonum-cycle

Sig~ is needed for combining values. If you were to attach two Int. or Float number boxes to a Cycle~ object, only the most recently changed number box would affect the frequency of the Cycle~ object.

If you ran the two number boxes into two Sig~ objects and then patch them into a Cycle~, the frequency of Cycle~ would be the SUM of the two number boxes.

Sometimes it's perfectly fine to just use Int. or Float number boxes to control objects, but sometimes using Sig~ is necessary, like with Frequency Modulation synthesis.

Check out MSP Tutorials 4 (Routing Signals) and 11 (Frequency Modulation) for a few examples.

Here's a stripped down FM patch with a few notes on how and where Sig~ is needed in order for the patch to work:

difference between sig->cycle and flonum->cycle?