[Audacity-nyquist] How do I create a local instead of a global variable?

[David S. <dav...@vc...>]

I want to replace many instances of setting global variables
containing sound (using setq) with let. I have looked at several
examples of code but don't understand how to use let.

If for example I have

(setq variable-name expression)

how would I convert that global variable code into local variable
code using let?

Thanks very much

David