diff --git a/doomsday/apps/plugins/common/include/g_common.h b/doomsday/apps/plugins/common/include/g_common.h
index 118df9849b..872b62bf1a 100644
--- a/doomsday/apps/plugins/common/include/g_common.h
+++ b/doomsday/apps/plugins/common/include/g_common.h
@@ -96,7 +96,7 @@ de::String G_EpisodeTitle(de::String episodeId);
  *
  * @todo: Should use WorldSystem::mapInfoForMapUri() instead.
  */
-de::Record const &G_MapInfoForMapUri(de::Uri const &mapUri);
+de::Record &G_MapInfoForMapUri(de::Uri const &mapUri);
 
 /**
  * @param mapUri  Identifier of the map to lookup the author of.
diff --git a/doomsday/apps/plugins/common/src/game/g_game.cpp b/doomsday/apps/plugins/common/src/game/g_game.cpp
index e4d9b3066b..1ae5db908f 100644
--- a/doomsday/apps/plugins/common/src/game/g_game.cpp
+++ b/doomsday/apps/plugins/common/src/game/g_game.cpp
@@ -2088,15 +2088,15 @@ de::Uri G_ComposeMapUri(uint episode, uint map)
     return de::Uri("Maps", mapId);
 }
 
-Record const &G_MapInfoForMapUri(de::Uri const &mapUri)
+Record &G_MapInfoForMapUri(de::Uri const &mapUri)
 {
     // Is there a MapInfo definition for the given URI?
-    if (Record const *def = Defs().mapInfos.tryFind("id", mapUri.compose()))
+    if (Record *def = Defs().mapInfos.tryFind("id", mapUri.compose()))
     {
         return *def;
     }
     // Is there is a default definition (for all maps)?
-    if (Record const *def = Defs().mapInfos.tryFind("id", de::Uri("Maps", Path("*")).compose()))
+    if (Record *def = Defs().mapInfos.tryFind("id", de::Uri("Maps", Path("*")).compose()))
     {
         return *def;
     }
diff --git a/doomsday/apps/plugins/common/src/world/p_sound.cpp b/doomsday/apps/plugins/common/src/world/p_sound.cpp
index 442dd8aa64..0ba4299f50 100644
--- a/doomsday/apps/plugins/common/src/world/p_sound.cpp
+++ b/doomsday/apps/plugins/common/src/world/p_sound.cpp
@@ -115,10 +115,19 @@ void SndInfoParser(ddstring_s const *path)
 
                 if(mapNumber > 0)
                 {
-                    Record const &mapInfo = G_MapInfoForMapUri(G_ComposeMapUri(0, mapNumber - 1));
-                    if(Record *music = Defs().musics.tryFind("id", mapInfo.gets("music")))
+                    Record &mapInfo = G_MapInfoForMapUri(G_ComposeMapUri(0, mapNumber - 1));
+                    if (const Record *music = Defs().musics.tryFind("id", Str_Text(lumpName)))
                     {
-                        music->set("lumpName", Str_Text(lumpName));
+                        // There is a music definition with this ID, let's use that.
+                        mapInfo.set("music", Str_Text(lumpName));
+                    }
+                    else
+                    {
+                        // Modify the map's currently used music to override the music lump.
+                        if (Record *music = Defs().musics.tryFind("id", mapInfo.gets("music")))
+                        {
+                            music->set("lumpName", Str_Text(lumpName));
+                        }
                     }
                 }
                 continue;
diff --git a/doomsday/apps/plugins/importidtech1/src/mapinfotranslator.cpp b/doomsday/apps/plugins/importidtech1/src/mapinfotranslator.cpp
index b2319d6568..9bb6eebfc9 100644
--- a/doomsday/apps/plugins/importidtech1/src/mapinfotranslator.cpp
+++ b/doomsday/apps/plugins/importidtech1/src/mapinfotranslator.cpp
@@ -1415,35 +1415,47 @@ DENG2_PIMPL_NOREF(MapInfoTranslator)
         for(auto const pair : defs.mapInfos)
         {
             MapInfo const &info = pair.second;
-            if(custom != info.getb("custom")) continue;
+
+            const bool isCustomMapInfo = info.getb("custom");
+
+            if(custom != isCustomMapInfo) continue;
 
             de::Uri mapUri(info.gets("id"), RC_NULL);
-            if(mapUri.path().isEmpty()) continue;
+            if (mapUri.path().isEmpty()) continue;
 
-            String const mapId = toMapId(mapUri);
+            const String mapId         = toMapId(mapUri);
+            const String musicLumpName = info.gets("music");
+            bool         addedMusicDef = false;
 
-            String const musicId = mapId + "_music";
-            os << "\n\nMusic {"
-               << "\n  ID = \"" + musicId + "\";";
-            String const musicLumpName = info.gets("music");
-            if(!musicLumpName.isEmpty())
+            if (isCustomMapInfo && (!musicLumpName.isEmpty() || info.geti("cdTrack")))
             {
-               os << "\n  Lump = \"" + musicLumpName + "\";";
+                addedMusicDef = true;
+
+                // Add a music def for this custom music.
+                os << "\n\nMusic {"
+                   << "\n  ID = \"" + mapId + "\";"; // music ID == map ID
+                if (!musicLumpName.isEmpty())
+                {
+                   os << "\n  Lump = \"" + musicLumpName + "\";";
+                }
+                os << "\n  CD Track = " << info.geti("cdTrack") << ";"
+                   << "\n}";
             }
-            os << "\n  CD Track = " + String::number(info.geti("cdTrack")) + ";"
-               << "\n}";
 
-            bool const doubleSky = info.getb("doubleSky");
+            const bool doubleSky = info.getb("doubleSky");
 
             os << "\n\nMap Info {"
                << "\n  ID = \"" + mapId + "\";"
                << "\n  Title = \"" + info.gets("title") + "\";";
-            if(!info.getb("custom"))
+            if (!isCustomMapInfo)
             {
                os << "\n  Author = \"" + String(Str_Text(gameInfo.author)) + "\";";
             }
-            os << "\n  Fade Table = \"" + info.gets("fadeTable") + "\";"
-               << "\n  Music = \"" + musicId + "\";";
+            os << "\n  Fade Table = \"" + info.gets("fadeTable") + "\";";
+            if (addedMusicDef)
+            {
+                os << "\n  Music = \"" + mapId + "\";";
+            }
             de::Uri titleImageUri(info.gets("titleImage"), RC_NULL);
             if(!titleImageUri.path().isEmpty())
             {