A wrapper for Softalk. This Emacs lisp can be used on only Windows.

softalk.el

(defvar softalk-command (concat (replace-regexp-in-string
                                 "\\\\" "/" (getenv "INST_DIR"))
                                "/home/src/softalk/SofTalk.exe"))
(defvar softalk-speed 100)
(defvar softalk-volume 100)

(defun softalk-text (text)
  (deferred:$
    (deferred:process "sh" "-c"
      (format "%s /X:1 /V:%s /S:%s /W: %s"
              softalk-command softalk-volume softalk-speed text))))

(defun softalk-region (start end)
  (interactive "r")
  (softalk-text
   (replace-regexp-in-string
    "\n" "" (buffer-substring-no-properties start end))))