diff --git a/.gitmodules b/.gitmodules
index 29a834d8..68ea45db 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -843,3 +843,6 @@
 [submodule "repos/PitchGrid"]
 	path = repos/PitchGrid
 	url = https://github.com/peterjungx/PitchGridRack.git
+[submodule "repos/NullSet"]
+	path = repos/NullSet
+	url = https://github.com/nicholas-j-denning/NullSet.git
diff --git a/repos/NullSet b/repos/NullSet
new file mode 160000
index 00000000..3637d338
--- /dev/null
+++ b/repos/NullSet
@@ -0,0 +1 @@
+Subproject commit 3637d33896d66c4aa0abb0e0e7e3e42f1fd3acb9