mtk_attach_gtk_hscale (c1, gui1->hscale);
 mtk_attach_gtk_vscale (c2, gui1->vscale);
 mtk_attach_gtk_hscale (c2, gui2->hscale);
 ... 
Sorry, I meant :
midibind_attach_gtk_hscale (c1, gui1->hscale);
midibind_attach_gtk_vscale (c2, gui1->vscale);
midibind_attach_gtk_hscale (c2, gui2->hscale);
...
--
   og