diff --git a/churchtools_api/events.py b/churchtools_api/events.py
index ff7200f..4d442c7 100644
--- a/churchtools_api/events.py
+++ b/churchtools_api/events.py
@@ -666,7 +666,9 @@ def get_event_masterdata(
 
         Keywords:
             resultClass: str with name of the masterdata type (not datatype) common
-             types are 'absenceReasons', 'songCategories', 'services', 'serviceGroups'
+             types are 'absenceReasons', 'songCategories', 'songSources'
+            'services', 'serviceGroups', 'facts'
+
             returnAsDict: if the list with one type should be returned as dict by ID
 
         Returns:
diff --git a/churchtools_api/songs.py b/churchtools_api/songs.py
index 2a39bbf..7c4b212 100644
--- a/churchtools_api/songs.py
+++ b/churchtools_api/songs.py
@@ -148,23 +148,10 @@ def lookup_song_category_as_id(self, category_name: str) -> int:
     def get_song_source_map(self) -> dict:
         """Requesting CT metadata for mapping of song sources.
 
-        WARNING - uses undocumented AJAX API.
-
         Returns:
             a dictionary of {Index:{valuedict}}.
         """
-        # TODO @bensteUEM: implement using REST API once support case 135796 is resolved
-        # https://github.com/bensteUEM/ChurchToolsAPI/issues/124
-        logging.warning(
-            "Using undocumented AJAX API"
-            " because function does not exist as REST endpoint"
-        )
-        url = self.domain + "/index.php?q=churchservice/ajax"
-        headers = {"accept": "application/json"}
-        data = {"func": "getMasterData"}
-        response = self.session.post(url=url, headers=headers, data=data)
-        response_content = json.loads(response.content)
-        return response_content["data"]["songsource"]
+        return self.get_event_masterdata(resultClass="songSources", returnAsDict=True)
 
     def lookup_song_source_as_id(
         self, longname: str | None = None, shortname: str | None = None
diff --git a/tests/test_churchtools_api_events.py b/tests/test_churchtools_api_events.py
index 8f04df0..6b8712d 100644
--- a/tests/test_churchtools_api_events.py
+++ b/tests/test_churchtools_api_events.py
@@ -225,24 +225,37 @@ def test_get_set_event_admins(self) -> None:
 
         assert self.api.set_event_admins_ajax(SAMPLE_EVENT_ID, EXPECTED_ADMIN_IDS)
 
-    def test_get_event_masterdata(self) -> None:
-        """IMPORTANT - This test method and the parameters used depend on target system!
-
-        Tries to get a list of event masterdata and a type of masterdata from CT
-        The values depend on your system data! -
-        Test case is valid against ELKW1610.KRZ.TOOLS
-        """
-        result = self.api.get_event_masterdata()
-        EXPECTED_KEYS = [
+    @pytest.mark.parametrize(
+        ("expected_key"),
+        [
             "absenceReasons",
             "facts",
             "songCategories",
             "songSources",
             "services",
             "serviceGroups",
-        ]
-        assert set(result) == set(EXPECTED_KEYS)
+        ],
+    )
+    def test_get_event_masterdata_all(self, expected_key: str) -> None:
+        """Tries to get a list of event masterdata and a type of masterdata from CT.
+
+        Categories should exist on all systems with CT version 116 or newer
 
+        Args:
+            expected_key: the expected key
+        """
+        result_all = self.api.get_event_masterdata()
+        result_specific = self.api.get_event_masterdata(resultClass=expected_key)
+        assert expected_key in result_all
+        assert len(result_specific) >= 1
+
+    def test_get_event_masterdata_specific(self) -> None:
+        """IMPORTANT - This test method and the parameters used depend on target system!
+
+        Tries to get a list of event masterdata and a type of masterdata from CT
+        The values depend on your system data! -
+        Test case is valid against ELKW1610.KRZ.TOOLS
+        """
         result = self.api.get_event_masterdata(resultClass="serviceGroups")
         assert len(result) > 1
         assert result[0]["name"] == "Programm"
diff --git a/tests/test_churchtools_api_songs.py b/tests/test_churchtools_api_songs.py
index c287638..4cd5adb 100644
--- a/tests/test_churchtools_api_songs.py
+++ b/tests/test_churchtools_api_songs.py
@@ -329,8 +329,6 @@ def test_lookup_song_source_as_id(self, caplog: pytest.LogCaptureFixture) -> Non
             result = self.api.lookup_song_source_as_id()
         assert result is None
         EXPECTED_MESSAGES = [
-            "Using undocumented AJAX API"
-            " because function does not exist as REST endpoint",
             "missing argument longname or shortname required",
         ]
         assert caplog.messages == EXPECTED_MESSAGES