Initial implementation that doesn't quite work

README.md

@@ -1,2 +1,9 @@
 # selectric-mode
-Make your Emacs sound like a proper typewriter.
+
+Make your Emacs sound like a proper typewriter. Extremely useful if you
+have a puny, silent, rubberish, non-clicky keyboard.
+
+The sound of the typewriter was recorded by a person nicknamed
+"secretmojo" and is available on
+https://www.freesound.org/people/secretmojo/sounds/224012/ under a
+Creative Commons license.

selectric-mode.el

@@ -0,0 +1,55 @@
+;;; selectric-mode.el --- IBM Selectric mode for Emacs  -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2015  Ricardo Bánffy
+
+;; Author: Ricardo Bánffy <rbanffy@gmail.com>
+;; Keywords: multimedia, convenience, typewriter, selectric
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This minor mode plays the sound of an IBM Selectric typewriter as
+;; you type.
+
+;;; Code:
+
+(defun selectric-type-sound ()
+  (start-process-shell-command
+   "*Messages*" nil (format "aplay %sselectric-type.wav"
+                            (file-name-directory load-file-name))))
+
+(define-minor-mode selectric-mode
+  "Toggle Selectric mode.
+Interactively with no argument, this command toggles the mode.
+A positive prefix argument enables the mode, any other prefix
+argument disables it.  From Lisp, argument omitted or nil enables
+the mode, `toggle' toggles the state.
+
+When Selectric mode is enabled, your Emacs will sound like an IBM
+Selectric typewriter."
+  :global t
+  ;; The initial value.
+  :init-value nil
+  ;; The indicator for the mode line.
+  :lighter " Selectric"
+  :group 'selectric
+
+  (if selectric-mode
+      (add-hook 'post-self-insert-hook 'selectric-type-sound)
+    (remove-hook 'post-self-insert-hook 'selectric-type-sound))
+  )
+
+(provide 'selectric-mode)
+;;; selectric-mode.el ends here