gnu: Add non-session-manager.

* gnu/packages/music.scm (non-session-manager): New variable.

gnu/packages/music.scm

@@ -639,6 +639,28 @@ Sequencer happens on-line, in real-time.  Music can be composed live, while the
 transport is rolling.")
       (license license:gpl2+))))
 
+(define-public non-session-manager
+  (package (inherit non-sequencer)
+    (name "non-session-manager")
+    (arguments
+     (substitute-keyword-arguments (package-arguments non-sequencer)
+       ((#:configure-flags flags)
+        `(cons "--project=session-manager"
+               (delete "--project=sequencer" ,flags)))))
+    (inputs
+     `(("jack" ,jack-1)
+       ("liblo" ,liblo)
+       ("ntk" ,ntk)))
+    (native-inputs
+     `(("pkg-config" ,pkg-config)))
+    (home-page "http://non.tuxfamily.org/nsm/")
+    (synopsis "Audio session management")
+    (description
+     "The Non Session Manager is an API and an implementation for audio
+session management.  NSM clients use a well-specified OSC protocol to
+communicate with the session management daemon.")
+    (license license:gpl2+)))
+
 (define-public solfege
   (package
     (name "solfege")