добавил many=True в сериализатор избранных треков

server/proj/audio/serializers.py

@@ -14,6 +14,6 @@ class FavoriteSongSerializer(serializers.ModelSerializer):
     def to_representation(self, instance):
         rep = super().to_representation(instance)
         rep["song"] = SongSerializer(
-            instance.song).data
+            instance.song, many=True).data
         return rep
         

server/proj/audio/views.py

@@ -20,7 +20,7 @@ class SongViewSet(ViewSet):
     def list(self, request):
         user_pk = request.user.pk
         queryset = get_list_or_404(FavoriteSong, user=user_pk)
-        serializer = SongSerializer(queryset, many=True)
+        serializer = FavoriteSongSerializer(queryset, many=True)
         return Response(serializer.data)
     
     def retrieve(self, request, pk=None):