fix

code/modules/instruments/songs/_song.dm

@@ -307,9 +307,15 @@
 /datum/song/holoparasite
 	var/mob/living/simple_animal/hostile/guardian/stand
 
+/datum/song/holoparasite/New(atom/parent, list/instrument_ids)
+	. = ..()
+	stand = istype(parent, /mob/living/simple_animal/hostile/guardian) && parent
+
 /datum/song/holoparasite/updateDialog()
 	stand.ui_interact(src)
 
 /datum/song/holoparasite/should_stop_playing(mob/user)
 	return FALSE
 
+/datum/song/holoparasite/check_can_use(mob/user)
+	return user == stand)

code/modules/instruments/songs/editor.dm

@@ -109,8 +109,11 @@
 				linenum++
 		updateDialog(usr)		// make sure updates when complete
 
+/datum/song/proc/check_can_use(mob/user)
+	return user.canUseTopic(parent, TRUE, FALSE, FALSE, FALSE)
+
 /datum/song/Topic(href, href_list)
-	if(!usr.canUseTopic(parent, TRUE, FALSE, FALSE, FALSE))
+	if(!check_can_use(usr))
 		usr << browse(null, "window=instrument")
 		usr.unset_machine()
 		return