I have a few schemes installed on my computer (MIT, guile, chicken), but when I run such code as this

#+BEGIN_SRC scheme :session one

(define (myadd x y)

(+ x y))

#+END_SRC

it works -- beautifully with multiple REPLs (as you name them in the :session) -- but it always grabs the guile. I'd like it to use chicken instead -- or maybe later MIT. I've got latest geiser installed as well that should handle chicken. How can I use chicken inside of orgmode scheme code blocks? Wild guess, guile is first on some list, i.e., path? babel customize didn't seem to have an entry for which flavor.