Wait.... I just woke up which has been shown to be a bad time to post to the list, but isn't FilterBasic a sort of utility class that the other filters and (some?) delays inherit from but which shouldn't be instantiated on it's own?

At any rate, I'm fairly sure FilterBasic is one of the filters that doesn't come with a ready-made .freq() and instead needs coefficients to be set, If that's what you want that would indeed be a very good use of functions but get "Filter" (or one like PoleZero, BiQuad.....) instead. You may also want to get a serious text on DSP, read that until your head hurts, get your local friendly mathematician and get him coffee, listen to him until your head hurts....

....then most likely decide you are very happy there are people like Ge and Perry who can sort such matters for you ;¬).

In the meantime I looked it up; FilterBasic isn't in the Ugen list but "Filter" is and "Filter" is as versatile and open-ended as they come so there is no actual need to instantiate "FilterBasic" at all.