Chicken indeed interoperates with C quite easily and productively. You're right that the generated C code is mostly incomprehensible to humans, but compiles without difficulty.

The Chicken C API has functions/macros that return values and those that don't return. The former include the fabulous embedded API (crunch is an altogether different beast) which I've used in "mixed language" programming to good effect. In such cases Scheme is rather like the essential "glue" that enables the parts written in other languages to work as a whole.

Of course becoming proficient in Scheme programming takes time and effort. I believe it's true that some brains have an affinity for Lispy languages while others don't. Fortunately, there are many ways to write programs to accomplish a given task.